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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>9.9. Date/Time Functions and Operators</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="functions-formatting.html" title="9.8. Data Type Formatting Functions" /><link rel="next" href="functions-enum.html" title="9.10. Enum Support Functions" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.9. Date/Time Functions and Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-formatting.html" title="9.8. Data Type Formatting Functions">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><th width="60%" align="center">Chapter 9. Functions and Operators</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-enum.html" title="9.10. Enum Support Functions">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-DATETIME"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.9. Date/Time Functions and Operators</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT">9.9.1. <code class="function">EXTRACT</code>, <code class="function">date_part</code></a></span></dt><dt><span class="sect2"><a href="functions-datetime.html#FUNCTIONS-DATETIME-TRUNC">9.9.2. <code class="function">date_trunc</code></a></span></dt><dt><span class="sect2"><a href="functions-datetime.html#FUNCTIONS-DATETIME-ZONECONVERT">9.9.3. <code class="literal">AT TIME ZONE</code></a></span></dt><dt><span class="sect2"><a href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT">9.9.4. Current Date/Time</a></span></dt><dt><span class="sect2"><a href="functions-datetime.html#FUNCTIONS-DATETIME-DELAY">9.9.5. Delaying Execution</a></span></dt></dl></div><p>

  3.    <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-TABLE" title="Table 9.31. Date/Time Functions">Table 9.31</a> shows the available

  4.    functions for date/time value processing, with details appearing in

  5.    the following subsections.  <a class="xref" href="functions-datetime.html#OPERATORS-DATETIME-TABLE" title="Table 9.30. Date/Time Operators">Table 9.30</a> illustrates the behaviors of

  6.    the basic arithmetic operators (<code class="literal">+</code>,

  7.    <code class="literal">*</code>, etc.).  For formatting functions, refer to

  8.    <a class="xref" href="functions-formatting.html" title="9.8. Data Type Formatting Functions">Section 9.8</a>.  You should be familiar with

  9.    the background information on date/time data types from <a class="xref" href="datatype-datetime.html" title="8.5. Date/Time Types">Section 8.5</a>.

  10.   </p><p>

  11.    All the functions and operators described below that take <code class="type">time</code> or <code class="type">timestamp</code>

  12.    inputs actually come in two variants: one that takes <code class="type">time with time zone</code> or <code class="type">timestamp

  13.    with time zone</code>, and one that takes <code class="type">time without time zone</code> or <code class="type">timestamp without time zone</code>.

  14.    For brevity, these variants are not shown separately.  Also, the

  15.    <code class="literal">+</code> and <code class="literal">*</code> operators come in commutative pairs (for

  16.    example both date + integer and integer + date); we show only one of each

  17.    such pair.

  18.   </p><div class="table" id="OPERATORS-DATETIME-TABLE"><p class="title"><strong>Table 9.30. Date/Time Operators</strong></p><div class="table-contents"><table class="table" summary="Date/Time Operators" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Operator</th><th>Example</th><th>Result</th></tr></thead><tbody><tr><td> <code class="literal">+</code> </td><td><code class="literal">date '2001-09-28' + integer '7'</code></td><td><code class="literal">date '2001-10-05'</code></td></tr><tr><td> <code class="literal">+</code> </td><td><code class="literal">date '2001-09-28' + interval '1 hour'</code></td><td><code class="literal">timestamp '2001-09-28 01:00:00'</code></td></tr><tr><td> <code class="literal">+</code> </td><td><code class="literal">date '2001-09-28' + time '03:00'</code></td><td><code class="literal">timestamp '2001-09-28 03:00:00'</code></td></tr><tr><td> <code class="literal">+</code> </td><td><code class="literal">interval '1 day' + interval '1 hour'</code></td><td><code class="literal">interval '1 day 01:00:00'</code></td></tr><tr><td> <code class="literal">+</code> </td><td><code class="literal">timestamp '2001-09-28 01:00' + interval '23 hours'</code></td><td><code class="literal">timestamp '2001-09-29 00:00:00'</code></td></tr><tr><td> <code class="literal">+</code> </td><td><code class="literal">time '01:00' + interval '3 hours'</code></td><td><code class="literal">time '04:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">- interval '23 hours'</code></td><td><code class="literal">interval '-23:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">date '2001-10-01' - date '2001-09-28'</code></td><td><code class="literal">integer '3'</code> (days)</td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">date '2001-10-01' - integer '7'</code></td><td><code class="literal">date '2001-09-24'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">date '2001-09-28' - interval '1 hour'</code></td><td><code class="literal">timestamp '2001-09-27 23:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">time '05:00' - time '03:00'</code></td><td><code class="literal">interval '02:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">time '05:00' - interval '2 hours'</code></td><td><code class="literal">time '03:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">timestamp '2001-09-28 23:00' - interval '23 hours'</code></td><td><code class="literal">timestamp '2001-09-28 00:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">interval '1 day' - interval '1 hour'</code></td><td><code class="literal">interval '1 day -01:00:00'</code></td></tr><tr><td> <code class="literal">-</code> </td><td><code class="literal">timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'</code></td><td><code class="literal">interval '1 day 15:00:00'</code></td></tr><tr><td> <code class="literal">*</code> </td><td><code class="literal">900 * interval '1 second'</code></td><td><code class="literal">interval '00:15:00'</code></td></tr><tr><td> <code class="literal">*</code> </td><td><code class="literal">21 * interval '1 day'</code></td><td><code class="literal">interval '21 days'</code></td></tr><tr><td> <code class="literal">*</code> </td><td><code class="literal">double precision '3.5' * interval '1 hour'</code></td><td><code class="literal">interval '03:30:00'</code></td></tr><tr><td> <code class="literal">/</code> </td><td><code class="literal">interval '1 hour' / double precision '1.5'</code></td><td><code class="literal">interval '00:40:00'</code></td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="FUNCTIONS-DATETIME-TABLE"><p class="title"><strong>Table 9.31. Date/Time Functions</strong></p><div class="table-contents"><table class="table" summary="Date/Time Functions" border="1"><colgroup><col /><col /><col /><col /><col /></colgroup><thead><tr><th>Function</th><th>Return Type</th><th>Description</th><th>Example</th><th>Result</th></tr></thead><tbody><tr><td>

  19.          <a id="id-1.5.8.14.5.2.2.1.1.1" class="indexterm"></a>

  20.          <code class="literal"><code class="function">age(<code class="type">timestamp</code>, <code class="type">timestamp</code>)</code></code>

  21.         </td><td><code class="type">interval</code></td><td>Subtract arguments, producing a <span class="quote">“<span class="quote">symbolic</span>”</span> result that

  22.         uses years and months, rather than just days</td><td><code class="literal">age(timestamp '2001-04-10', timestamp '1957-06-13')</code></td><td><code class="literal">43 years 9 mons 27 days</code></td></tr><tr><td><code class="literal"><code class="function">age(<code class="type">timestamp</code>)</code></code></td><td><code class="type">interval</code></td><td>Subtract from <code class="function">current_date</code> (at midnight)</td><td><code class="literal">age(timestamp '1957-06-13')</code></td><td><code class="literal">43 years 8 mons 3 days</code></td></tr><tr><td>

  23.          <a id="id-1.5.8.14.5.2.2.3.1.1" class="indexterm"></a>

  24.          <code class="literal"><code class="function">clock_timestamp()</code></code>

  25.         </td><td><code class="type">timestamp with time zone</code></td><td>Current date and time (changes during statement execution);

  26.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  27.         </td><td> </td><td> </td></tr><tr><td>

  28.          <a id="id-1.5.8.14.5.2.2.4.1.1" class="indexterm"></a>

  29.          <code class="literal"><code class="function">current_date</code></code>

  30.         </td><td><code class="type">date</code></td><td>Current date;

  31.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  32.         </td><td> </td><td> </td></tr><tr><td>

  33.          <a id="id-1.5.8.14.5.2.2.5.1.1" class="indexterm"></a>

  34.          <code class="literal"><code class="function">current_time</code></code>

  35.         </td><td><code class="type">time with time zone</code></td><td>Current time of day;

  36.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  37.         </td><td> </td><td> </td></tr><tr><td>

  38.          <a id="id-1.5.8.14.5.2.2.6.1.1" class="indexterm"></a>

  39.          <code class="literal"><code class="function">current_timestamp</code></code>

  40.         </td><td><code class="type">timestamp with time zone</code></td><td>Current date and time (start of current transaction);

  41.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  42.         </td><td> </td><td> </td></tr><tr><td>

  43.          <a id="id-1.5.8.14.5.2.2.7.1.1" class="indexterm"></a>

  44.          <code class="literal"><code class="function">date_part(<code class="type">text</code>, <code class="type">timestamp</code>)</code></code>

  45.         </td><td><code class="type">double precision</code></td><td>Get subfield (equivalent to <code class="function">extract</code>);

  46.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT" title="9.9.1. EXTRACT, date_part">Section 9.9.1</a>

  47.         </td><td><code class="literal">date_part('hour', timestamp '2001-02-16 20:38:40')</code></td><td><code class="literal">20</code></td></tr><tr><td><code class="literal"><code class="function">date_part(<code class="type">text</code>, <code class="type">interval</code>)</code></code></td><td><code class="type">double precision</code></td><td>Get subfield (equivalent to

  48.          <code class="function">extract</code>); see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT" title="9.9.1. EXTRACT, date_part">Section 9.9.1</a>

  49.         </td><td><code class="literal">date_part('month', interval '2 years 3 months')</code></td><td><code class="literal">3</code></td></tr><tr><td>

  50.          <a id="id-1.5.8.14.5.2.2.9.1.1" class="indexterm"></a>

  51.          <code class="literal"><code class="function">date_trunc(<code class="type">text</code>, <code class="type">timestamp</code>)</code></code>

  52.         </td><td><code class="type">timestamp</code></td><td>Truncate to specified precision; see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-TRUNC" title="9.9.2. date_trunc">Section 9.9.2</a>

  53.         </td><td><code class="literal">date_trunc('hour', timestamp '2001-02-16 20:38:40')</code></td><td><code class="literal">2001-02-16 20:00:00</code></td></tr><tr><td><code class="literal"><code class="function">date_trunc(<code class="type">text</code>, <code class="type">timestamp with time zone</code>, <code class="type">text</code>)</code></code></td><td><code class="type">timestamp with time zone</code></td><td>Truncate to specified precision in the specified time zone; see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-TRUNC" title="9.9.2. date_trunc">Section 9.9.2</a>

  54.         </td><td><code class="literal">date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney')</code></td><td><code class="literal">2001-02-16 13:00:00+00</code></td></tr><tr><td><code class="literal"><code class="function">date_trunc(<code class="type">text</code>, <code class="type">interval</code>)</code></code></td><td><code class="type">interval</code></td><td>Truncate to specified precision; see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-TRUNC" title="9.9.2. date_trunc">Section 9.9.2</a>

  55.         </td><td><code class="literal">date_trunc('hour', interval '2 days 3 hours 40 minutes')</code></td><td><code class="literal">2 days 03:00:00</code></td></tr><tr><td>

  56.          <a id="id-1.5.8.14.5.2.2.12.1.1" class="indexterm"></a>

  57.          <code class="literal"><code class="function">extract</code>(<em class="parameter"><code>field</code></em> from

  58.          <code class="type">timestamp</code>)</code>

  59.         </td><td><code class="type">double precision</code></td><td>Get subfield; see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT" title="9.9.1. EXTRACT, date_part">Section 9.9.1</a>

  60.         </td><td><code class="literal">extract(hour from timestamp '2001-02-16 20:38:40')</code></td><td><code class="literal">20</code></td></tr><tr><td><code class="literal"><code class="function">extract</code>(<em class="parameter"><code>field</code></em> from

  61.          <code class="type">interval</code>)</code></td><td><code class="type">double precision</code></td><td>Get subfield; see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT" title="9.9.1. EXTRACT, date_part">Section 9.9.1</a>

  62.         </td><td><code class="literal">extract(month from interval '2 years 3 months')</code></td><td><code class="literal">3</code></td></tr><tr><td>

  63.          <a id="id-1.5.8.14.5.2.2.14.1.1" class="indexterm"></a>

  64.          <code class="literal"><code class="function">isfinite(<code class="type">date</code>)</code></code>

  65.         </td><td><code class="type">boolean</code></td><td>Test for finite date (not +/-infinity)</td><td><code class="literal">isfinite(date '2001-02-16')</code></td><td><code class="literal">true</code></td></tr><tr><td><code class="literal"><code class="function">isfinite(<code class="type">timestamp</code>)</code></code></td><td><code class="type">boolean</code></td><td>Test for finite time stamp (not +/-infinity)</td><td><code class="literal">isfinite(timestamp '2001-02-16 21:28:30')</code></td><td><code class="literal">true</code></td></tr><tr><td><code class="literal"><code class="function">isfinite(<code class="type">interval</code>)</code></code></td><td><code class="type">boolean</code></td><td>Test for finite interval</td><td><code class="literal">isfinite(interval '4 hours')</code></td><td><code class="literal">true</code></td></tr><tr><td>

  66.          <a id="id-1.5.8.14.5.2.2.17.1.1" class="indexterm"></a>

  67.          <code class="literal"><code class="function">justify_days(<code class="type">interval</code>)</code></code>

  68.         </td><td><code class="type">interval</code></td><td>Adjust interval so 30-day time periods are represented as months</td><td><code class="literal">justify_days(interval '35 days')</code></td><td><code class="literal">1 mon 5 days</code></td></tr><tr><td>

  69.          <a id="id-1.5.8.14.5.2.2.18.1.1" class="indexterm"></a>

  70.          <code class="literal"><code class="function">justify_hours(<code class="type">interval</code>)</code></code>

  71.         </td><td><code class="type">interval</code></td><td>Adjust interval so 24-hour time periods are represented as days</td><td><code class="literal">justify_hours(interval '27 hours')</code></td><td><code class="literal">1 day 03:00:00</code></td></tr><tr><td>

  72.          <a id="id-1.5.8.14.5.2.2.19.1.1" class="indexterm"></a>

  73.          <code class="literal"><code class="function">justify_interval(<code class="type">interval</code>)</code></code>

  74.         </td><td><code class="type">interval</code></td><td>Adjust interval using <code class="function">justify_days</code> and <code class="function">justify_hours</code>, with additional sign adjustments</td><td><code class="literal">justify_interval(interval '1 mon -1 hour')</code></td><td><code class="literal">29 days 23:00:00</code></td></tr><tr><td>

  75.          <a id="id-1.5.8.14.5.2.2.20.1.1" class="indexterm"></a>

  76.          <code class="literal"><code class="function">localtime</code></code>

  77.         </td><td><code class="type">time</code></td><td>Current time of day;

  78.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  79.         </td><td> </td><td> </td></tr><tr><td>

  80.          <a id="id-1.5.8.14.5.2.2.21.1.1" class="indexterm"></a>

  81.          <code class="literal"><code class="function">localtimestamp</code></code>

  82.         </td><td><code class="type">timestamp</code></td><td>Current date and time (start of current transaction);

  83.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  84.         </td><td> </td><td> </td></tr><tr><td>

  85.          <a id="id-1.5.8.14.5.2.2.22.1.1" class="indexterm"></a>

  86.          <code class="literal">

  87.             <code class="function">

  88.              make_date(<em class="parameter"><code>year</code></em> <code class="type">int</code>,

  89.              <em class="parameter"><code>month</code></em> <code class="type">int</code>,

  90.              <em class="parameter"><code>day</code></em> <code class="type">int</code>)

  91.             </code>

  92.          </code>

  93.         </td><td><code class="type">date</code></td><td>

  94.          Create date from year, month and day fields

  95.         </td><td><code class="literal">make_date(2013, 7, 15)</code></td><td><code class="literal">2013-07-15</code></td></tr><tr><td>

  96.          <a id="id-1.5.8.14.5.2.2.23.1.1" class="indexterm"></a>

  97.          <code class="literal">

  98.           <code class="function">

  99.            make_interval(<em class="parameter"><code>years</code></em> <code class="type">int</code> DEFAULT 0,

  100.            <em class="parameter"><code>months</code></em> <code class="type">int</code> DEFAULT 0,

  101.            <em class="parameter"><code>weeks</code></em> <code class="type">int</code> DEFAULT 0,

  102.            <em class="parameter"><code>days</code></em> <code class="type">int</code> DEFAULT 0,

  103.            <em class="parameter"><code>hours</code></em> <code class="type">int</code> DEFAULT 0,

  104.            <em class="parameter"><code>mins</code></em> <code class="type">int</code> DEFAULT 0,

  105.            <em class="parameter"><code>secs</code></em> <code class="type">double precision</code> DEFAULT 0.0)

  106.           </code>

  107.          </code>

  108.         </td><td><code class="type">interval</code></td><td>

  109.          Create interval from years, months, weeks, days, hours, minutes and

  110.          seconds fields

  111.         </td><td><code class="literal">make_interval(days =&gt; 10)</code></td><td><code class="literal">10 days</code></td></tr><tr><td>

  112.          <a id="id-1.5.8.14.5.2.2.24.1.1" class="indexterm"></a>

  113.          <code class="literal">

  114.           <code class="function">

  115.            make_time(<em class="parameter"><code>hour</code></em> <code class="type">int</code>,

  116.            <em class="parameter"><code>min</code></em> <code class="type">int</code>,

  117.            <em class="parameter"><code>sec</code></em> <code class="type">double precision</code>)

  118.           </code>

  119.          </code>

  120.         </td><td><code class="type">time</code></td><td>

  121.          Create time from hour, minute and seconds fields

  122.         </td><td><code class="literal">make_time(8, 15, 23.5)</code></td><td><code class="literal">08:15:23.5</code></td></tr><tr><td>

  123.          <a id="id-1.5.8.14.5.2.2.25.1.1" class="indexterm"></a>

  124.          <code class="literal">

  125.           <code class="function">

  126.            make_timestamp(<em class="parameter"><code>year</code></em> <code class="type">int</code>,

  127.            <em class="parameter"><code>month</code></em> <code class="type">int</code>,

  128.            <em class="parameter"><code>day</code></em> <code class="type">int</code>,

  129.            <em class="parameter"><code>hour</code></em> <code class="type">int</code>,

  130.            <em class="parameter"><code>min</code></em> <code class="type">int</code>,

  131.            <em class="parameter"><code>sec</code></em> <code class="type">double precision</code>)

  132.           </code>

  133.          </code>

  134.         </td><td><code class="type">timestamp</code></td><td>

  135.          Create timestamp from year, month, day, hour, minute and seconds fields

  136.         </td><td><code class="literal">make_timestamp(2013, 7, 15, 8, 15, 23.5)</code></td><td><code class="literal">2013-07-15 08:15:23.5</code></td></tr><tr><td>

  137.          <a id="id-1.5.8.14.5.2.2.26.1.1" class="indexterm"></a>

  138.          <code class="literal">

  139.           <code class="function">

  140.            make_timestamptz(<em class="parameter"><code>year</code></em> <code class="type">int</code>,

  141.            <em class="parameter"><code>month</code></em> <code class="type">int</code>,

  142.            <em class="parameter"><code>day</code></em> <code class="type">int</code>,

  143.            <em class="parameter"><code>hour</code></em> <code class="type">int</code>,

  144.            <em class="parameter"><code>min</code></em> <code class="type">int</code>,

  145.            <em class="parameter"><code>sec</code></em> <code class="type">double precision</code>,

  146.            [<span class="optional"> <em class="parameter"><code>timezone</code></em> <code class="type">text</code> </span>])

  147.           </code>

  148.          </code>

  149.         </td><td><code class="type">timestamp with time zone</code></td><td>

  150.          Create timestamp with time zone from year, month, day, hour, minute

  151.          and seconds fields; if <em class="parameter"><code>timezone</code></em> is not

  152.          specified, the current time zone is used

  153.         </td><td><code class="literal">make_timestamptz(2013, 7, 15, 8, 15, 23.5)</code></td><td><code class="literal">2013-07-15 08:15:23.5+01</code></td></tr><tr><td>

  154.          <a id="id-1.5.8.14.5.2.2.27.1.1" class="indexterm"></a>

  155.          <code class="literal"><code class="function">now()</code></code>

  156.         </td><td><code class="type">timestamp with time zone</code></td><td>Current date and time (start of current transaction);

  157.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  158.         </td><td> </td><td> </td></tr><tr><td>

  159.          <a id="id-1.5.8.14.5.2.2.28.1.1" class="indexterm"></a>

  160.          <code class="literal"><code class="function">statement_timestamp()</code></code>

  161.         </td><td><code class="type">timestamp with time zone</code></td><td>Current date and time (start of current statement);

  162.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  163.         </td><td> </td><td> </td></tr><tr><td>

  164.          <a id="id-1.5.8.14.5.2.2.29.1.1" class="indexterm"></a>

  165.          <code class="literal"><code class="function">timeofday()</code></code>

  166.         </td><td><code class="type">text</code></td><td>Current date and time

  167.          (like <code class="function">clock_timestamp</code>, but as a <code class="type">text</code> string);

  168.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  169.         </td><td> </td><td> </td></tr><tr><td>

  170.          <a id="id-1.5.8.14.5.2.2.30.1.1" class="indexterm"></a>

  171.          <code class="literal"><code class="function">transaction_timestamp()</code></code>

  172.         </td><td><code class="type">timestamp with time zone</code></td><td>Current date and time (start of current transaction);

  173.          see <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-CURRENT" title="9.9.4. Current Date/Time">Section 9.9.4</a>

  174.         </td><td> </td><td> </td></tr><tr><td>

  175.          <a id="id-1.5.8.14.5.2.2.31.1.1" class="indexterm"></a>

  176.          <code class="literal"><code class="function">to_timestamp(<code class="type">double precision</code>)</code></code>

  177.         </td><td><code class="type">timestamp with time zone</code></td><td>Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to

  178.          timestamp</td><td><code class="literal">to_timestamp(1284352323)</code></td><td><code class="literal">2010-09-13 04:32:03+00</code></td></tr></tbody></table></div></div><br class="table-break" /><p>

  179.     <a id="id-1.5.8.14.6.1" class="indexterm"></a>

  180.     In addition to these functions, the SQL <code class="literal">OVERLAPS</code> operator is

  181.     supported:

  182. </p><pre class="synopsis">

  183. (<em class="replaceable"><code>start1</code></em>, <em class="replaceable"><code>end1</code></em>) OVERLAPS (<em class="replaceable"><code>start2</code></em>, <em class="replaceable"><code>end2</code></em>)

  184. (<em class="replaceable"><code>start1</code></em>, <em class="replaceable"><code>length1</code></em>) OVERLAPS (<em class="replaceable"><code>start2</code></em>, <em class="replaceable"><code>length2</code></em>)

  185. </pre><p>

  186.     This expression yields true when two time periods (defined by their

  187.     endpoints) overlap, false when they do not overlap.  The endpoints

  188.     can be specified as pairs of dates, times, or time stamps; or as

  189.     a date, time, or time stamp followed by an interval.  When a pair

  190.     of values is provided, either the start or the end can be written

  191.     first; <code class="literal">OVERLAPS</code> automatically takes the earlier value

  192.     of the pair as the start.  Each time period is considered to

  193.     represent the half-open interval <em class="replaceable"><code>start</code></em> <code class="literal">&lt;=</code>

  194.     <em class="replaceable"><code>time</code></em> <code class="literal">&lt;</code> <em class="replaceable"><code>end</code></em>, unless

  195.     <em class="replaceable"><code>start</code></em> and <em class="replaceable"><code>end</code></em> are equal in which case it

  196.     represents that single time instant.  This means for instance that two

  197.     time periods with only an endpoint in common do not overlap.

  198.    </p><pre class="screen">

  199. SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS

  200.        (DATE '2001-10-30', DATE '2002-10-30');

  201. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">true</code>

  202. SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS

  203.        (DATE '2001-10-30', DATE '2002-10-30');

  204. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">false</code>

  205. SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS

  206.        (DATE '2001-10-30', DATE '2001-10-31');

  207. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">false</code>

  208. SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS

  209.        (DATE '2001-10-30', DATE '2001-10-31');

  210. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">true</code>

  211. </pre><p>

  212.    When adding an <code class="type">interval</code> value to (or subtracting an

  213.    <code class="type">interval</code> value from) a <code class="type">timestamp with time zone</code>

  214.    value, the days component advances or decrements the date of the

  215.    <code class="type">timestamp with time zone</code> by the indicated number of days,

  216.    keeping the time of day the same.

  217.    Across daylight saving time changes (when the session time zone is set to a

  218.    time zone that recognizes DST), this means <code class="literal">interval '1 day'</code>

  219.    does not necessarily equal <code class="literal">interval '24 hours'</code>.

  220.    For example, with the session time zone set

  221.    to <code class="literal">America/Denver</code>:

  222. </p><pre class="screen">

  223. SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day';

  224. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2005-04-03 12:00:00-06</code>

  225. SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours';

  226. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2005-04-03 13:00:00-06</code>

  227. </pre><p>

  228.    This happens because an hour was skipped due to a change in daylight saving

  229.    time at <code class="literal">2005-04-03 02:00:00</code> in time zone

  230.    <code class="literal">America/Denver</code>.

  231.   </p><p>

  232.    Note there can be ambiguity in the <code class="literal">months</code> field returned by

  233.    <code class="function">age</code> because different months have different numbers of

  234.    days.  <span class="productname">PostgreSQL</span>'s approach uses the month from the

  235.    earlier of the two dates when calculating partial months.  For example,

  236.    <code class="literal">age('2004-06-01', '2004-04-30')</code> uses April to yield

  237.    <code class="literal">1 mon 1 day</code>, while using May would yield <code class="literal">1 mon 2

  238.    days</code> because May has 31 days, while April has only 30.

  239.   </p><p>

  240.    Subtraction of dates and timestamps can also be complex.  One conceptually

  241.    simple way to perform subtraction is to convert each value to a number

  242.    of seconds using <code class="literal">EXTRACT(EPOCH FROM ...)</code>, then subtract the

  243.    results; this produces the

  244.    number of <span class="emphasis"><em>seconds</em></span> between the two values.  This will adjust

  245.    for the number of days in each month, timezone changes, and daylight

  246.    saving time adjustments.  Subtraction of date or timestamp

  247.    values with the <span class="quote">“<span class="quote"><code class="literal">-</code></span>”</span> operator

  248.    returns the number of days (24-hours) and hours/minutes/seconds

  249.    between the values, making the same adjustments.  The <code class="function">age</code>

  250.    function returns years, months, days, and hours/minutes/seconds,

  251.    performing field-by-field subtraction and then adjusting for negative

  252.    field values.  The following queries illustrate the differences in these

  253.    approaches.  The sample results were produced with <code class="literal">timezone

  254.    = 'US/Eastern'</code>; there is a daylight saving time change between the

  255.    two dates used:

  256.   </p><pre class="screen">

  257. SELECT EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') -

  258.        EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00');

  259. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">10537200</code>

  260. SELECT (EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') -

  261.         EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00'))

  262.         / 60 / 60 / 24;

  263. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">121.958333333333</code>

  264. SELECT timestamptz '2013-07-01 12:00:00' - timestamptz '2013-03-01 12:00:00';

  265. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">121 days 23:00:00</code>

  266. SELECT age(timestamptz '2013-07-01 12:00:00', timestamptz '2013-03-01 12:00:00');

  267. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">4 mons</code>

  268. </pre><div class="sect2" id="FUNCTIONS-DATETIME-EXTRACT"><div class="titlepage"><div><div><h3 class="title">9.9.1. <code class="function">EXTRACT</code>, <code class="function">date_part</code></h3></div></div></div><a id="id-1.5.8.14.12.2" class="indexterm"></a><a id="id-1.5.8.14.12.3" class="indexterm"></a><pre class="synopsis">

  269. EXTRACT(<em class="replaceable"><code>field</code></em> FROM <em class="replaceable"><code>source</code></em>)

  270. </pre><p>

  271.     The <code class="function">extract</code> function retrieves subfields

  272.     such as year or hour from date/time values.

  273.     <em class="replaceable"><code>source</code></em> must be a value expression of

  274.     type <code class="type">timestamp</code>, <code class="type">time</code>, or <code class="type">interval</code>.

  275.     (Expressions of type <code class="type">date</code> are

  276.     cast to <code class="type">timestamp</code> and can therefore be used as

  277.     well.)  <em class="replaceable"><code>field</code></em> is an identifier or

  278.     string that selects what field to extract from the source value.

  279.     The <code class="function">extract</code> function returns values of type

  280.     <code class="type">double precision</code>.

  281.     The following are valid field names:

  282. 

  283.     

  284.     </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">century</code></span></dt><dd><p>

  285.         The century

  286.        </p><pre class="screen">

  287. SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13');

  288. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">20</code>

  289. SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40');

  290. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">21</code>

  291. </pre><p>

  292.         The first century starts at 0001-01-01 00:00:00 AD, although

  293.         they did not know it at the time. This definition applies to all

  294.         Gregorian calendar countries. There is no century number 0,

  295.         you go from -1 century to 1 century.

  296. 

  297.         If you disagree with this, please write your complaint to:

  298.         Pope, Cathedral Saint-Peter of Roma, Vatican.

  299.        </p></dd><dt><span class="term"><code class="literal">day</code></span></dt><dd><p>

  300.         For <code class="type">timestamp</code> values, the day (of the month) field

  301.         (1 - 31) ; for <code class="type">interval</code> values, the number of days

  302.        </p><pre class="screen">

  303. SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40');

  304. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">16</code>

  305. 

  306. SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute');

  307. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">40</code>

  308. </pre></dd><dt><span class="term"><code class="literal">decade</code></span></dt><dd><p>

  309.         The year field divided by 10

  310.        </p><pre class="screen">

  311. SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40');

  312. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">200</code>

  313. </pre></dd><dt><span class="term"><code class="literal">dow</code></span></dt><dd><p>

  314.         The day of the week as Sunday (<code class="literal">0</code>) to

  315.         Saturday (<code class="literal">6</code>)

  316.        </p><pre class="screen">

  317. SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40');

  318. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">5</code>

  319. </pre><p>

  320.         Note that <code class="function">extract</code>'s day of the week numbering

  321.         differs from that of the <code class="function">to_char(...,

  322.         'D')</code> function.

  323.        </p></dd><dt><span class="term"><code class="literal">doy</code></span></dt><dd><p>

  324.         The day of the year (1 - 365/366)

  325.        </p><pre class="screen">

  326. SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');

  327. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">47</code>

  328. </pre></dd><dt><span class="term"><code class="literal">epoch</code></span></dt><dd><p>

  329.         For <code class="type">timestamp with time zone</code> values, the

  330.         number of seconds since 1970-01-01 00:00:00 UTC (can be negative);

  331.         for <code class="type">date</code> and <code class="type">timestamp</code> values, the

  332.         number of seconds since 1970-01-01 00:00:00 local time;

  333.         for <code class="type">interval</code> values, the total number

  334.         of seconds in the interval

  335.        </p><pre class="screen">

  336. SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08');

  337. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">982384720.12</code>

  338. 

  339. SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');

  340. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">442800</code>

  341. </pre><p>

  342.         You can convert an epoch value back to a time stamp

  343.         with <code class="function">to_timestamp</code>:

  344.        </p><pre class="screen">

  345. SELECT to_timestamp(982384720.12);

  346. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-17 04:38:40.12+00</code>

  347. </pre></dd><dt><span class="term"><code class="literal">hour</code></span></dt><dd><p>

  348.         The hour field (0 - 23)

  349.        </p><pre class="screen">

  350. SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40');

  351. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">20</code>

  352. </pre></dd><dt><span class="term"><code class="literal">isodow</code></span></dt><dd><p>

  353.         The day of the week as Monday (<code class="literal">1</code>) to

  354.         Sunday (<code class="literal">7</code>)

  355.        </p><pre class="screen">

  356. SELECT EXTRACT(ISODOW FROM TIMESTAMP '2001-02-18 20:38:40');

  357. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">7</code>

  358. </pre><p>

  359.         This is identical to <code class="literal">dow</code> except for Sunday.  This

  360.         matches the <acronym class="acronym">ISO</acronym> 8601 day of the week numbering.

  361.        </p></dd><dt><span class="term"><code class="literal">isoyear</code></span></dt><dd><p>

  362.         The <acronym class="acronym">ISO</acronym> 8601 week-numbering year that the date

  363.         falls in (not applicable to intervals)

  364.        </p><pre class="screen">

  365. SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-01');

  366. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2005</code>

  367. SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-02');

  368. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2006</code>

  369. </pre><p>

  370.         Each <acronym class="acronym">ISO</acronym> 8601 week-numbering year begins with the

  371.         Monday of the week containing the 4th of January, so in early

  372.         January or late December the <acronym class="acronym">ISO</acronym> year may be

  373.         different from the Gregorian year.  See the <code class="literal">week</code>

  374.         field for more information.

  375.        </p><p>

  376.         This field is not available in PostgreSQL releases prior to 8.3.

  377.        </p></dd><dt><span class="term"><code class="literal">microseconds</code></span></dt><dd><p>

  378.         The seconds field, including fractional parts, multiplied by 1

  379.         000 000;  note that this includes full seconds

  380.        </p><pre class="screen">

  381. SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5');

  382. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">28500000</code>

  383. </pre></dd><dt><span class="term"><code class="literal">millennium</code></span></dt><dd><p>

  384.         The millennium

  385.        </p><pre class="screen">

  386. SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40');

  387. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">3</code>

  388. </pre><p>

  389.         Years in the 1900s are in the second millennium.

  390.         The third millennium started January 1, 2001.

  391.        </p></dd><dt><span class="term"><code class="literal">milliseconds</code></span></dt><dd><p>

  392.         The seconds field, including fractional parts, multiplied by

  393.         1000.  Note that this includes full seconds.

  394.        </p><pre class="screen">

  395. SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5');

  396. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">28500</code>

  397. </pre></dd><dt><span class="term"><code class="literal">minute</code></span></dt><dd><p>

  398.         The minutes field (0 - 59)

  399.        </p><pre class="screen">

  400. SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40');

  401. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">38</code>

  402. </pre></dd><dt><span class="term"><code class="literal">month</code></span></dt><dd><p>

  403.         For <code class="type">timestamp</code> values, the number of the month

  404.         within the year (1 - 12) ; for <code class="type">interval</code> values,

  405.         the number of months, modulo 12 (0 - 11)

  406.        </p><pre class="screen">

  407. SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40');

  408. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2</code>

  409. 

  410. SELECT EXTRACT(MONTH FROM INTERVAL '2 years 3 months');

  411. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">3</code>

  412. 

  413. SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months');

  414. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">1</code>

  415. </pre></dd><dt><span class="term"><code class="literal">quarter</code></span></dt><dd><p>

  416.         The quarter of the year (1 - 4) that the date is in

  417.        </p><pre class="screen">

  418. SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40');

  419. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">1</code>

  420. </pre></dd><dt><span class="term"><code class="literal">second</code></span></dt><dd><p>

  421.         The seconds field, including fractional parts (0 -

  422.         59<a href="#ftn.id-1.5.8.14.12.5.11.16.2.1.1" class="footnote"><sup class="footnote" id="id-1.5.8.14.12.5.11.16.2.1.1">[7]</sup></a>)

  423.        </p><pre class="screen">

  424. SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40');

  425. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">40</code>

  426. 

  427. SELECT EXTRACT(SECOND FROM TIME '17:12:28.5');

  428. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">28.5</code>

  429. </pre></dd><dt><span class="term"><code class="literal">timezone</code></span></dt><dd><p>

  430.         The time zone offset from UTC, measured in seconds.  Positive values

  431.         correspond to time zones east of UTC, negative values to

  432.         zones west of UTC.  (Technically,

  433.         <span class="productname">PostgreSQL</span> does not use UTC because

  434.         leap seconds are not handled.)

  435.        </p></dd><dt><span class="term"><code class="literal">timezone_hour</code></span></dt><dd><p>

  436.         The hour component of the time zone offset

  437.        </p></dd><dt><span class="term"><code class="literal">timezone_minute</code></span></dt><dd><p>

  438.         The minute component of the time zone offset

  439.        </p></dd><dt><span class="term"><code class="literal">week</code></span></dt><dd><p>

  440.         The number of the <acronym class="acronym">ISO</acronym> 8601 week-numbering week of

  441.         the year.  By definition, ISO weeks start on Mondays and the first

  442.         week of a year contains January 4 of that year.  In other words, the

  443.         first Thursday of a year is in week 1 of that year.

  444.        </p><p>

  445.         In the ISO week-numbering system, it is possible for early-January

  446.         dates to be part of the 52nd or 53rd week of the previous year, and for

  447.         late-December dates to be part of the first week of the next year.

  448.         For example, <code class="literal">2005-01-01</code> is part of the 53rd week of year

  449.         2004, and <code class="literal">2006-01-01</code> is part of the 52nd week of year

  450.         2005, while <code class="literal">2012-12-31</code> is part of the first week of 2013.

  451.         It's recommended to use the <code class="literal">isoyear</code> field together with

  452.         <code class="literal">week</code> to get consistent results.

  453.        </p><pre class="screen">

  454. SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40');

  455. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">7</code>

  456. </pre></dd><dt><span class="term"><code class="literal">year</code></span></dt><dd><p>

  457.         The year field.  Keep in mind there is no <code class="literal">0 AD</code>, so subtracting

  458.         <code class="literal">BC</code> years from <code class="literal">AD</code> years should be done with care.

  459.        </p><pre class="screen">

  460. SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40');

  461. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001</code>

  462. </pre></dd></dl></div><p>

  463.    </p><div class="note"><h3 class="title">Note</h3><p>

  464.      When the input value is +/-Infinity, <code class="function">extract</code> returns

  465.      +/-Infinity for monotonically-increasing fields (<code class="literal">epoch</code>,

  466.      <code class="literal">julian</code>, <code class="literal">year</code>, <code class="literal">isoyear</code>,

  467.      <code class="literal">decade</code>, <code class="literal">century</code>, and <code class="literal">millennium</code>).

  468.      For other fields, NULL is returned.  <span class="productname">PostgreSQL</span>

  469.      versions before 9.6 returned zero for all cases of infinite input.

  470.     </p></div><p>

  471.     The <code class="function">extract</code> function is primarily intended

  472.     for computational processing.  For formatting date/time values for

  473.     display, see <a class="xref" href="functions-formatting.html" title="9.8. Data Type Formatting Functions">Section 9.8</a>.

  474.    </p><p>

  475.     The <code class="function">date_part</code> function is modeled on the traditional

  476.     <span class="productname">Ingres</span> equivalent to the

  477.     <acronym class="acronym">SQL</acronym>-standard function <code class="function">extract</code>:

  478. </p><pre class="synopsis">

  479. date_part('<em class="replaceable"><code>field</code></em>', <em class="replaceable"><code>source</code></em>)

  480. </pre><p>

  481.     Note that here the <em class="replaceable"><code>field</code></em> parameter needs to

  482.     be a string value, not a name.  The valid field names for

  483.     <code class="function">date_part</code> are the same as for

  484.     <code class="function">extract</code>.

  485.    </p><pre class="screen">

  486. SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');

  487. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">16</code>

  488. 

  489. SELECT date_part('hour', INTERVAL '4 hours 3 minutes');

  490. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">4</code>

  491. </pre></div><div class="sect2" id="FUNCTIONS-DATETIME-TRUNC"><div class="titlepage"><div><div><h3 class="title">9.9.2. <code class="function">date_trunc</code></h3></div></div></div><a id="id-1.5.8.14.13.2" class="indexterm"></a><p>

  492.     The function <code class="function">date_trunc</code> is conceptually

  493.     similar to the <code class="function">trunc</code> function for numbers.

  494.    </p><p>

  495. </p><pre class="synopsis">

  496. date_trunc(<em class="replaceable"><code>field</code></em>, <em class="replaceable"><code>source</code></em> [, <em class="replaceable"><code>time_zone</code></em> ])

  497. </pre><p>

  498.     <em class="replaceable"><code>source</code></em> is a value expression of type

  499.     <code class="type">timestamp</code>, <code class="type">timestamp with time zone</code>,

  500.     or <code class="type">interval</code>.

  501.     (Values of type <code class="type">date</code> and

  502.     <code class="type">time</code> are cast automatically to <code class="type">timestamp</code> or

  503.     <code class="type">interval</code>, respectively.)

  504.     <em class="replaceable"><code>field</code></em> selects to which precision to

  505.     truncate the input value.  The return value is likewise of type

  506.     <code class="type">timestamp</code>, <code class="type">timestamp with time zone</code>,

  507.     or <code class="type">interval</code>,

  508.     and it has all fields that are less significant than the

  509.     selected one set to zero (or one, for day and month).

  510.    </p><p>

  511.     Valid values for <em class="replaceable"><code>field</code></em> are:

  512.     </p><table border="0" summary="Simple list" class="simplelist"><tr><td><code class="literal">microseconds</code></td></tr><tr><td><code class="literal">milliseconds</code></td></tr><tr><td><code class="literal">second</code></td></tr><tr><td><code class="literal">minute</code></td></tr><tr><td><code class="literal">hour</code></td></tr><tr><td><code class="literal">day</code></td></tr><tr><td><code class="literal">week</code></td></tr><tr><td><code class="literal">month</code></td></tr><tr><td><code class="literal">quarter</code></td></tr><tr><td><code class="literal">year</code></td></tr><tr><td><code class="literal">decade</code></td></tr><tr><td><code class="literal">century</code></td></tr><tr><td><code class="literal">millennium</code></td></tr></table><p>

  513.    </p><p>

  514.     When the input value is of type <code class="type">timestamp with time zone</code>,

  515.     the truncation is performed with respect to a particular time zone;

  516.     for example, truncation to <code class="literal">day</code> produces a value that

  517.     is midnight in that zone.  By default, truncation is done with respect

  518.     to the current <a class="xref" href="runtime-config-client.html#GUC-TIMEZONE">TimeZone</a> setting, but the

  519.     optional <em class="replaceable"><code>time_zone</code></em> argument can be provided

  520.     to specify a different time zone.  The time zone name can be specified

  521.     in any of the ways described in <a class="xref" href="datatype-datetime.html#DATATYPE-TIMEZONES" title="8.5.3. Time Zones">Section 8.5.3</a>.

  522.    </p><p>

  523.     A time zone cannot be specified when processing <code class="type">timestamp without

  524.     time zone</code> or <code class="type">interval</code> inputs.  These are always

  525.     taken at face value.

  526.    </p><p>

  527.     Examples (assuming the local time zone is <code class="literal">America/New_York</code>):

  528. </p><pre class="screen">

  529. SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');

  530. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 20:00:00</code>

  531. 

  532. SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');

  533. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-01-01 00:00:00</code>

  534. 

  535. SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00');

  536. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 00:00:00-05</code>

  537. 

  538. SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney');

  539. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 08:00:00-05</code>

  540. 

  541. SELECT date_trunc('hour', INTERVAL '3 days 02:47:33');

  542. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">3 days 02:00:00</code>

  543. </pre><p>

  544.    </p></div><div class="sect2" id="FUNCTIONS-DATETIME-ZONECONVERT"><div class="titlepage"><div><div><h3 class="title">9.9.3. <code class="literal">AT TIME ZONE</code></h3></div></div></div><a id="id-1.5.8.14.14.2" class="indexterm"></a><a id="id-1.5.8.14.14.3" class="indexterm"></a><p>

  545.     The <code class="literal">AT TIME ZONE</code> converts time

  546.     stamp <span class="emphasis"><em>without time zone</em></span> to/from

  547.     time stamp <span class="emphasis"><em>with time zone</em></span>, and

  548.     <span class="emphasis"><em>time</em></span> values to different time zones. <a class="xref" href="functions-datetime.html#FUNCTIONS-DATETIME-ZONECONVERT-TABLE" title="Table 9.32. AT TIME ZONE Variants">Table 9.32</a> shows its variants.

  549.    </p><div class="table" id="FUNCTIONS-DATETIME-ZONECONVERT-TABLE"><p class="title"><strong>Table 9.32. <code class="literal">AT TIME ZONE</code> Variants</strong></p><div class="table-contents"><table class="table" summary="AT TIME ZONE Variants" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Expression</th><th>Return Type</th><th>Description</th></tr></thead><tbody><tr><td>

  550.          <code class="literal"><code class="type">timestamp without time zone</code> AT TIME ZONE <em class="replaceable"><code>zone</code></em></code>

  551.         </td><td><code class="type">timestamp with time zone</code></td><td>Treat given time stamp <span class="emphasis"><em>without time zone</em></span> as located in the specified time zone</td></tr><tr><td>

  552.          <code class="literal"><code class="type">timestamp with time zone</code> AT TIME ZONE <em class="replaceable"><code>zone</code></em></code>

  553.         </td><td><code class="type">timestamp without time zone</code></td><td>Convert given time stamp <span class="emphasis"><em>with time zone</em></span> to the new time

  554.         zone, with no time zone designation</td></tr><tr><td>

  555.          <code class="literal"><code class="type">time with time zone</code> AT TIME ZONE <em class="replaceable"><code>zone</code></em></code>

  556.         </td><td><code class="type">time with time zone</code></td><td>Convert given time <span class="emphasis"><em>with time zone</em></span> to the new time zone</td></tr></tbody></table></div></div><br class="table-break" /><p>

  557.     In these expressions, the desired time zone <em class="replaceable"><code>zone</code></em> can be

  558.     specified either as a text string (e.g., <code class="literal">'America/Los_Angeles'</code>)

  559.     or as an interval (e.g., <code class="literal">INTERVAL '-08:00'</code>).

  560.     In the text case, a time zone name can be specified in any of the ways

  561.     described in <a class="xref" href="datatype-datetime.html#DATATYPE-TIMEZONES" title="8.5.3. Time Zones">Section 8.5.3</a>.

  562.    </p><p>

  563.     Examples (assuming the local time zone is <code class="literal">America/Los_Angeles</code>):

  564. </p><pre class="screen">

  565. SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver';

  566. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 19:38:40-08</code>

  567. 

  568. SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver';

  569. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 18:38:40</code>

  570. 

  571. SELECT TIMESTAMP '2001-02-16 20:38:40-05' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago';

  572. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-02-16 05:38:40</code>

  573. </pre><p>

  574.     The first example adds a time zone to a value that lacks it, and

  575.     displays the value using the current <code class="varname">TimeZone</code>

  576.     setting.  The second example shifts the time stamp with time zone value

  577.     to the specified time zone, and returns the value without a time zone.

  578.     This allows storage and display of values different from the current

  579.     <code class="varname">TimeZone</code> setting.  The third example converts

  580.     Tokyo time to Chicago time.   Converting <span class="emphasis"><em>time</em></span>

  581.     values to other time zones uses the currently active time zone rules

  582.     since no date is supplied.

  583.    </p><p>

  584.     The function <code class="literal"><code class="function">timezone</code>(<em class="replaceable"><code>zone</code></em>,

  585.     <em class="replaceable"><code>timestamp</code></em>)</code> is equivalent to the SQL-conforming construct

  586.     <code class="literal"><em class="replaceable"><code>timestamp</code></em> AT TIME ZONE

  587.     <em class="replaceable"><code>zone</code></em></code>.

  588.    </p></div><div class="sect2" id="FUNCTIONS-DATETIME-CURRENT"><div class="titlepage"><div><div><h3 class="title">9.9.4. Current Date/Time</h3></div></div></div><a id="id-1.5.8.14.15.2" class="indexterm"></a><a id="id-1.5.8.14.15.3" class="indexterm"></a><p>

  589.     <span class="productname">PostgreSQL</span> provides a number of functions

  590.     that return values related to the current date and time.  These

  591.     SQL-standard functions all return values based on the start time of

  592.     the current transaction:

  593. </p><pre class="synopsis">

  594. CURRENT_DATE

  595. CURRENT_TIME

  596. CURRENT_TIMESTAMP

  597. CURRENT_TIME(<em class="replaceable"><code>precision</code></em>)

  598. CURRENT_TIMESTAMP(<em class="replaceable"><code>precision</code></em>)

  599. LOCALTIME

  600. LOCALTIMESTAMP

  601. LOCALTIME(<em class="replaceable"><code>precision</code></em>)

  602. LOCALTIMESTAMP(<em class="replaceable"><code>precision</code></em>)

  603. </pre><p>

  604.     </p><p>

  605.      <code class="function">CURRENT_TIME</code> and

  606.      <code class="function">CURRENT_TIMESTAMP</code> deliver values with time zone;

  607.      <code class="function">LOCALTIME</code> and

  608.      <code class="function">LOCALTIMESTAMP</code> deliver values without time zone.

  609.     </p><p>

  610.      <code class="function">CURRENT_TIME</code>,

  611.      <code class="function">CURRENT_TIMESTAMP</code>,

  612.      <code class="function">LOCALTIME</code>, and

  613.      <code class="function">LOCALTIMESTAMP</code>

  614.      can optionally take

  615.      a precision parameter, which causes the result to be rounded

  616.      to that many fractional digits in the seconds field.  Without a precision parameter,

  617.      the result is given to the full available precision.

  618.     </p><p>

  619.     Some examples:

  620. </p><pre class="screen">

  621. SELECT CURRENT_TIME;

  622. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">14:39:53.662522-05</code>

  623. 

  624. SELECT CURRENT_DATE;

  625. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-12-23</code>

  626. 

  627. SELECT CURRENT_TIMESTAMP;

  628. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-12-23 14:39:53.662522-05</code>

  629. 

  630. SELECT CURRENT_TIMESTAMP(2);

  631. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-12-23 14:39:53.66-05</code>

  632. 

  633. SELECT LOCALTIMESTAMP;

  634. <em class="lineannotation"><span class="lineannotation">Result: </span></em><code class="computeroutput">2001-12-23 14:39:53.662522</code>

  635. </pre><p>

  636.    </p><p>

  637.     Since these functions return

  638.     the start time of the current transaction, their values do not

  639.     change during the transaction. This is considered a feature:

  640.     the intent is to allow a single transaction to have a consistent

  641.     notion of the <span class="quote">“<span class="quote">current</span>”</span> time, so that multiple

  642.     modifications within the same transaction bear the same

  643.     time stamp.

  644.    </p><div class="note"><h3 class="title">Note</h3><p>

  645.      Other database systems might advance these values more

  646.      frequently.

  647.     </p></div><p>

  648.     <span class="productname">PostgreSQL</span> also provides functions that

  649.     return the start time of the current statement, as well as the actual

  650.     current time at the instant the function is called.  The complete list

  651.     of non-SQL-standard time functions is:

  652. </p><pre class="synopsis">

  653. transaction_timestamp()

  654. statement_timestamp()

  655. clock_timestamp()

  656. timeofday()

  657. now()

  658. </pre><p>

  659.    </p><p>

  660.     <code class="function">transaction_timestamp()</code> is equivalent to

  661.     <code class="function">CURRENT_TIMESTAMP</code>, but is named to clearly reflect

  662.     what it returns.

  663.     <code class="function">statement_timestamp()</code> returns the start time of the current

  664.     statement (more specifically, the time of receipt of the latest command

  665.     message from the client).

  666.     <code class="function">statement_timestamp()</code> and <code class="function">transaction_timestamp()</code>

  667.     return the same value during the first command of a transaction, but might

  668.     differ during subsequent commands.

  669.     <code class="function">clock_timestamp()</code> returns the actual current time, and

  670.     therefore its value changes even within a single SQL command.

  671.     <code class="function">timeofday()</code> is a historical

  672.     <span class="productname">PostgreSQL</span> function.  Like

  673.     <code class="function">clock_timestamp()</code>, it returns the actual current time,

  674.     but as a formatted <code class="type">text</code> string rather than a <code class="type">timestamp

  675.     with time zone</code> value.

  676.     <code class="function">now()</code> is a traditional <span class="productname">PostgreSQL</span>

  677.     equivalent to <code class="function">transaction_timestamp()</code>.

  678.    </p><p>

  679.     All the date/time data types also accept the special literal value

  680.     <code class="literal">now</code> to specify the current date and time (again,

  681.     interpreted as the transaction start time).  Thus,

  682.     the following three all return the same result:

  683. </p><pre class="programlisting">

  684. SELECT CURRENT_TIMESTAMP;

  685. SELECT now();

  686. SELECT TIMESTAMP 'now';  -- incorrect for use with DEFAULT

  687. </pre><p>

  688.    </p><div class="tip"><h3 class="title">Tip</h3><p>

  689.       You do not want to use the third form when specifying a <code class="literal">DEFAULT</code>

  690.       clause while creating a table.  The system will convert <code class="literal">now</code>

  691.       to a <code class="type">timestamp</code> as soon as the constant is parsed, so that when

  692.       the default value is needed,

  693.       the time of the table creation would be used!  The first two

  694.       forms will not be evaluated until the default value is used,

  695.       because they are function calls.  Thus they will give the desired

  696.       behavior of defaulting to the time of row insertion.

  697.      </p></div></div><div class="sect2" id="FUNCTIONS-DATETIME-DELAY"><div class="titlepage"><div><div><h3 class="title">9.9.5. Delaying Execution</h3></div></div></div><a id="id-1.5.8.14.16.2" class="indexterm"></a><a id="id-1.5.8.14.16.3" class="indexterm"></a><a id="id-1.5.8.14.16.4" class="indexterm"></a><a id="id-1.5.8.14.16.5" class="indexterm"></a><a id="id-1.5.8.14.16.6" class="indexterm"></a><p>

  698.     The following functions are available to delay execution of the server

  699.     process:

  700. </p><pre class="synopsis">

  701. pg_sleep(<em class="replaceable"><code>seconds</code></em>)

  702. pg_sleep_for(<code class="type">interval</code>)

  703. pg_sleep_until(<code class="type">timestamp with time zone</code>)

  704. </pre><p>

  705. 

  706.     <code class="function">pg_sleep</code> makes the current session's process

  707.     sleep until <em class="replaceable"><code>seconds</code></em> seconds have

  708.     elapsed.  <em class="replaceable"><code>seconds</code></em> is a value of type

  709.     <code class="type">double precision</code>, so fractional-second delays can be specified.

  710.     <code class="function">pg_sleep_for</code> is a convenience function for larger

  711.     sleep times specified as an <code class="type">interval</code>.

  712.     <code class="function">pg_sleep_until</code> is a convenience function for when

  713.     a specific wake-up time is desired.

  714.     For example:

  715. 

  716. </p><pre class="programlisting">

  717. SELECT pg_sleep(1.5);

  718. SELECT pg_sleep_for('5 minutes');

  719. SELECT pg_sleep_until('tomorrow 03:00');

  720. </pre><p>

  721.    </p><div class="note"><h3 class="title">Note</h3><p>

  722.       The effective resolution of the sleep interval is platform-specific;

  723.       0.01 seconds is a common value.  The sleep delay will be at least as long

  724.       as specified. It might be longer depending on factors such as server load.

  725.       In particular, <code class="function">pg_sleep_until</code> is not guaranteed to

  726.       wake up exactly at the specified time, but it will not wake up any earlier.

  727.      </p></div><div class="warning"><h3 class="title">Warning</h3><p>

  728.       Make sure that your session does not hold more locks than necessary

  729.       when calling <code class="function">pg_sleep</code> or its variants.  Otherwise

  730.       other sessions might have to wait for your sleeping process, slowing down

  731.       the entire system.

  732.      </p></div></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.id-1.5.8.14.12.5.11.16.2.1.1" class="footnote"><p><a href="#id-1.5.8.14.12.5.11.16.2.1.1" class="simpara"><sup class="simpara">[7] </sup></a>60 if leap seconds are

  733.         implemented by the operating system</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-formatting.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="functions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="functions-enum.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.8. Data Type Formatting Functions </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 9.10. Enum Support Functions</td></tr></table></div></body></html>
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