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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>9.18. Array 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-conditional.html" title="9.17. Conditional Expressions" /><link rel="next" href="functions-range.html" title="9.19. Range Functions and Operators" /></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">9.18. Array Functions and Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-conditional.html" title="9.17. Conditional Expressions">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-range.html" title="9.19. Range Functions and Operators">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-ARRAY"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.18. Array Functions and Operators</h2></div></div></div><p>

  3.    <a class="xref" href="functions-array.html#ARRAY-OPERATORS-TABLE" title="Table 9.51. Array Operators">Table 9.51</a> shows the operators

  4.    available for array types.

  5.   </p><div class="table" id="ARRAY-OPERATORS-TABLE"><p class="title"><strong>Table 9.51. Array Operators</strong></p><div class="table-contents"><table class="table" summary="Array Operators" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Operator</th><th>Description</th><th>Example</th><th>Result</th></tr></thead><tbody><tr><td> <code class="literal">=</code> </td><td>equal</td><td><code class="literal">ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&lt;&gt;</code> </td><td>not equal</td><td><code class="literal">ARRAY[1,2,3] &lt;&gt; ARRAY[1,2,4]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&lt;</code> </td><td>less than</td><td><code class="literal">ARRAY[1,2,3] &lt; ARRAY[1,2,4]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&gt;</code> </td><td>greater than</td><td><code class="literal">ARRAY[1,4,3] &gt; ARRAY[1,2,4]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&lt;=</code> </td><td>less than or equal</td><td><code class="literal">ARRAY[1,2,3] &lt;= ARRAY[1,2,3]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&gt;=</code> </td><td>greater than or equal</td><td><code class="literal">ARRAY[1,4,3] &gt;= ARRAY[1,4,3]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">@&gt;</code> </td><td>contains</td><td><code class="literal">ARRAY[1,4,3] @&gt; ARRAY[3,1,3]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&lt;@</code> </td><td>is contained by</td><td><code class="literal">ARRAY[2,2,7] &lt;@ ARRAY[1,7,4,2,6]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">&amp;&amp;</code> </td><td>overlap (have elements in common)</td><td><code class="literal">ARRAY[1,4,3] &amp;&amp; ARRAY[2,1]</code></td><td><code class="literal">t</code></td></tr><tr><td> <code class="literal">||</code> </td><td>array-to-array concatenation</td><td><code class="literal">ARRAY[1,2,3] || ARRAY[4,5,6]</code></td><td><code class="literal">{1,2,3,4,5,6}</code></td></tr><tr><td> <code class="literal">||</code> </td><td>array-to-array concatenation</td><td><code class="literal">ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]</code></td><td><code class="literal">{{1,2,3},{4,5,6},{7,8,9}}</code></td></tr><tr><td> <code class="literal">||</code> </td><td>element-to-array concatenation</td><td><code class="literal">3 || ARRAY[4,5,6]</code></td><td><code class="literal">{3,4,5,6}</code></td></tr><tr><td> <code class="literal">||</code> </td><td>array-to-element concatenation</td><td><code class="literal">ARRAY[4,5,6] || 7</code></td><td><code class="literal">{4,5,6,7}</code></td></tr></tbody></table></div></div><br class="table-break" /><p>

  6.    The array ordering operators (<code class="literal">&lt;</code>,

  7.    <code class="literal">&gt;=</code>, etc) compare the array contents

  8.    element-by-element, using the default B-tree comparison function for

  9.    the element data type, and sort based on the first difference.

  10.    In multidimensional arrays the elements are visited in row-major order

  11.    (last subscript varies most rapidly).

  12.    If the contents of two arrays are equal but the dimensionality is

  13.    different, the first difference in the dimensionality information

  14.    determines the sort order.  (This is a change from versions of

  15.    <span class="productname">PostgreSQL</span> prior to 8.2: older versions would claim

  16.    that two arrays with the same contents were equal, even if the

  17.    number of dimensions or subscript ranges were different.)

  18.   </p><p>

  19.    The array containment operators (<code class="literal">&lt;@</code>

  20.    and <code class="literal">@&gt;</code>) consider one array to be contained in

  21.    another one if each of its elements appears in the other one.

  22.    Duplicates are not treated specially, thus <code class="literal">ARRAY[1]</code>

  23.    and <code class="literal">ARRAY[1,1]</code> are each considered to contain the

  24.    other.

  25.   </p><p>

  26.    See <a class="xref" href="arrays.html" title="8.15. Arrays">Section 8.15</a> for more details about array operator

  27.    behavior.  See <a class="xref" href="indexes-types.html" title="11.2. Index Types">Section 11.2</a> for more details about

  28.    which operators support indexed operations.

  29.   </p><p>

  30.    <a class="xref" href="functions-array.html#ARRAY-FUNCTIONS-TABLE" title="Table 9.52. Array Functions">Table 9.52</a> shows the functions

  31.    available for use with array types. See <a class="xref" href="arrays.html" title="8.15. Arrays">Section 8.15</a>

  32.    for more information  and examples of the use of these functions.

  33.   </p><a id="id-1.5.8.23.8" class="indexterm"></a><a id="id-1.5.8.23.9" class="indexterm"></a><a id="id-1.5.8.23.10" class="indexterm"></a><a id="id-1.5.8.23.11" class="indexterm"></a><a id="id-1.5.8.23.12" class="indexterm"></a><a id="id-1.5.8.23.13" class="indexterm"></a><a id="id-1.5.8.23.14" class="indexterm"></a><a id="id-1.5.8.23.15" class="indexterm"></a><a id="id-1.5.8.23.16" class="indexterm"></a><a id="id-1.5.8.23.17" class="indexterm"></a><a id="id-1.5.8.23.18" class="indexterm"></a><a id="id-1.5.8.23.19" class="indexterm"></a><a id="id-1.5.8.23.20" class="indexterm"></a><a id="id-1.5.8.23.21" class="indexterm"></a><a id="id-1.5.8.23.22" class="indexterm"></a><a id="id-1.5.8.23.23" class="indexterm"></a><a id="id-1.5.8.23.24" class="indexterm"></a><div class="table" id="ARRAY-FUNCTIONS-TABLE"><p class="title"><strong>Table 9.52. Array Functions</strong></p><div class="table-contents"><table class="table" summary="Array 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>

  34.          <code class="literal">

  35.           <code class="function">array_append</code>(<code class="type">anyarray</code>, <code class="type">anyelement</code>)

  36.          </code>

  37.         </td><td><code class="type">anyarray</code></td><td>append an element to the end of an array</td><td><code class="literal">array_append(ARRAY[1,2], 3)</code></td><td><code class="literal">{1,2,3}</code></td></tr><tr><td>

  38.          <code class="literal">

  39.           <code class="function">array_cat</code>(<code class="type">anyarray</code>, <code class="type">anyarray</code>)

  40.          </code>

  41.         </td><td><code class="type">anyarray</code></td><td>concatenate two arrays</td><td><code class="literal">array_cat(ARRAY[1,2,3], ARRAY[4,5])</code></td><td><code class="literal">{1,2,3,4,5}</code></td></tr><tr><td>

  42.          <code class="literal">

  43.           <code class="function">array_ndims</code>(<code class="type">anyarray</code>)

  44.          </code>

  45.         </td><td><code class="type">int</code></td><td>returns the number of dimensions of the array</td><td><code class="literal">array_ndims(ARRAY[[1,2,3], [4,5,6]])</code></td><td><code class="literal">2</code></td></tr><tr><td>

  46.          <code class="literal">

  47.           <code class="function">array_dims</code>(<code class="type">anyarray</code>)

  48.          </code>

  49.         </td><td><code class="type">text</code></td><td>returns a text representation of array's dimensions</td><td><code class="literal">array_dims(ARRAY[[1,2,3], [4,5,6]])</code></td><td><code class="literal">[1:2][1:3]</code></td></tr><tr><td>

  50.          <code class="literal">

  51.           <code class="function">array_fill</code>(<code class="type">anyelement</code>, <code class="type">int[]</code>

  52.           [<span class="optional">, <code class="type">int[]</code></span>])

  53.          </code>

  54.         </td><td><code class="type">anyarray</code></td><td>returns an array initialized with supplied value and

  55.          dimensions, optionally with lower bounds other than 1</td><td><code class="literal">array_fill(7, ARRAY[3], ARRAY[2])</code></td><td><code class="literal">[2:4]={7,7,7}</code></td></tr><tr><td>

  56.          <code class="literal">

  57.           <code class="function">array_length</code>(<code class="type">anyarray</code>, <code class="type">int</code>)

  58.          </code>

  59.         </td><td><code class="type">int</code></td><td>returns the length of the requested array dimension</td><td><code class="literal">array_length(array[1,2,3], 1)</code></td><td><code class="literal">3</code></td></tr><tr><td>

  60.          <code class="literal">

  61.           <code class="function">array_lower</code>(<code class="type">anyarray</code>, <code class="type">int</code>)

  62.          </code>

  63.         </td><td><code class="type">int</code></td><td>returns lower bound of the requested array dimension</td><td><code class="literal">array_lower('[0:2]={1,2,3}'::int[], 1)</code></td><td><code class="literal">0</code></td></tr><tr><td>

  64.          <code class="literal">

  65.           <code class="function">array_position</code>(<code class="type">anyarray</code>, <code class="type">anyelement</code> [<span class="optional">, <code class="type">int</code></span>])

  66.          </code>

  67.         </td><td><code class="type">int</code></td><td>returns the subscript of the first occurrence of the second

  68.         argument in the array, starting at the element indicated by the third

  69.         argument or at the first element (array must be one-dimensional)</td><td><code class="literal">array_position(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon')</code></td><td><code class="literal">2</code></td></tr><tr><td>

  70.          <code class="literal">

  71.           <code class="function">array_positions</code>(<code class="type">anyarray</code>, <code class="type">anyelement</code>)

  72.          </code>

  73.         </td><td><code class="type">int[]</code></td><td>returns an array of subscripts of all occurrences of the second

  74.         argument in the array given as first argument (array must be

  75.         one-dimensional)</td><td><code class="literal">array_positions(ARRAY['A','A','B','A'], 'A')</code></td><td><code class="literal">{1,2,4}</code></td></tr><tr><td>

  76.          <code class="literal">

  77.           <code class="function">array_prepend</code>(<code class="type">anyelement</code>, <code class="type">anyarray</code>)

  78.          </code>

  79.         </td><td><code class="type">anyarray</code></td><td>append an element to the beginning of an array</td><td><code class="literal">array_prepend(1, ARRAY[2,3])</code></td><td><code class="literal">{1,2,3}</code></td></tr><tr><td>

  80.          <code class="literal">

  81.           <code class="function">array_remove</code>(<code class="type">anyarray</code>, <code class="type">anyelement</code>)

  82.          </code>

  83.         </td><td><code class="type">anyarray</code></td><td>remove all elements equal to the given value from the array

  84.          (array must be one-dimensional)</td><td><code class="literal">array_remove(ARRAY[1,2,3,2], 2)</code></td><td><code class="literal">{1,3}</code></td></tr><tr><td>

  85.          <code class="literal">

  86.           <code class="function">array_replace</code>(<code class="type">anyarray</code>, <code class="type">anyelement</code>, <code class="type">anyelement</code>)

  87.          </code>

  88.         </td><td><code class="type">anyarray</code></td><td>replace each array element equal to the given value with a new value</td><td><code class="literal">array_replace(ARRAY[1,2,5,4], 5, 3)</code></td><td><code class="literal">{1,2,3,4}</code></td></tr><tr><td>

  89.          <code class="literal">

  90.           <code class="function">array_to_string</code>(<code class="type">anyarray</code>, <code class="type">text</code> [<span class="optional">, <code class="type">text</code></span>])

  91.          </code>

  92.         </td><td><code class="type">text</code></td><td>concatenates array elements using supplied delimiter and

  93.          optional null string</td><td><code class="literal">array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')</code></td><td><code class="literal">1,2,3,*,5</code></td></tr><tr><td>

  94.          <code class="literal">

  95.           <code class="function">array_upper</code>(<code class="type">anyarray</code>, <code class="type">int</code>)

  96.          </code>

  97.         </td><td><code class="type">int</code></td><td>returns upper bound of the requested array dimension</td><td><code class="literal">array_upper(ARRAY[1,8,3,7], 1)</code></td><td><code class="literal">4</code></td></tr><tr><td>

  98.          <code class="literal">

  99.           <code class="function">cardinality</code>(<code class="type">anyarray</code>)

  100.          </code>

  101.         </td><td><code class="type">int</code></td><td>returns the total number of elements in the array, or 0 if the array is empty</td><td><code class="literal">cardinality(ARRAY[[1,2],[3,4]])</code></td><td><code class="literal">4</code></td></tr><tr><td>

  102.          <code class="literal">

  103.           <code class="function">string_to_array</code>(<code class="type">text</code>, <code class="type">text</code> [<span class="optional">, <code class="type">text</code></span>])

  104.          </code>

  105.         </td><td><code class="type">text[]</code></td><td>splits string into array elements using supplied delimiter and

  106.          optional null string</td><td><code class="literal">string_to_array('xx~^~yy~^~zz', '~^~', 'yy')</code></td><td><code class="literal">{xx,NULL,zz}</code></td></tr><tr><td>

  107.          <code class="literal">

  108.           <code class="function">unnest</code>(<code class="type">anyarray</code>)

  109.          </code>

  110.         </td><td><code class="type">setof anyelement</code></td><td>expand an array to a set of rows</td><td><code class="literal">unnest(ARRAY[1,2])</code></td><td><pre class="literallayout">1

  111. 2</pre>(2 rows)</td></tr><tr><td>

  112.          <code class="literal">

  113.           <code class="function">unnest</code>(<code class="type">anyarray</code>, <code class="type">anyarray</code> [, ...])

  114.          </code>

  115.         </td><td><code class="type">setof anyelement, anyelement [, ...]</code></td><td>expand multiple arrays (possibly of different types) to a set

  116.          of rows.  This is only allowed in the FROM clause; see

  117.          <a class="xref" href="queries-table-expressions.html#QUERIES-TABLEFUNCTIONS" title="7.2.1.4. Table Functions">Section 7.2.1.4</a></td><td><code class="literal">unnest(ARRAY[1,2],ARRAY['foo','bar','baz'])</code></td><td><pre class="literallayout">1    foo

  118. 2    bar

  119. NULL baz</pre>(3 rows)</td></tr></tbody></table></div></div><br class="table-break" /><p>

  120.     In <code class="function">array_position</code> and <code class="function">array_positions</code>,

  121.     each array element is compared to the searched value using

  122.     <code class="literal">IS NOT DISTINCT FROM</code> semantics.

  123.    </p><p>

  124.     In <code class="function">array_position</code>, <code class="literal">NULL</code> is returned

  125.     if the value is not found.

  126.    </p><p>

  127.     In <code class="function">array_positions</code>, <code class="literal">NULL</code> is returned

  128.     only if the array is <code class="literal">NULL</code>; if the value is not found in

  129.     the array, an empty array is returned instead.

  130.    </p><p>

  131.     In <code class="function">string_to_array</code>, if the delimiter parameter is

  132.     NULL, each character in the input string will become a separate element in

  133.     the resulting array.  If the delimiter is an empty string, then the entire

  134.     input string is returned as a one-element array.  Otherwise the input

  135.     string is split at each occurrence of the delimiter string.

  136.    </p><p>

  137.     In <code class="function">string_to_array</code>, if the null-string parameter

  138.     is omitted or NULL, none of the substrings of the input will be replaced

  139.     by NULL.

  140.     In <code class="function">array_to_string</code>, if the null-string parameter

  141.     is omitted or NULL, any null elements in the array are simply skipped

  142.     and not represented in the output string.

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

  144.      There are two differences in the behavior of <code class="function">string_to_array</code>

  145.      from pre-9.1 versions of <span class="productname">PostgreSQL</span>.

  146.      First, it will return an empty (zero-element) array rather than NULL when

  147.      the input string is of zero length.  Second, if the delimiter string is

  148.      NULL, the function splits the input into individual characters, rather

  149.      than returning NULL as before.

  150.     </p></div><p>

  151.     See also <a class="xref" href="functions-aggregate.html" title="9.20. Aggregate Functions">Section 9.20</a> about the aggregate

  152.     function <code class="function">array_agg</code> for use with arrays.

  153.    </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-conditional.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-range.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.17. Conditional Expressions </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 9.19. Range Functions and Operators</td></tr></table></div></body></html>
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