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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/tutorial-accessdb.html

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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>1.4. Accessing a Database</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="tutorial-createdb.html" title="1.3. Creating a Database" /><link rel="next" href="tutorial-sql.html" title="Chapter 2. The SQL Language" /></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">1.4. Accessing a Database</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="tutorial-createdb.html" title="1.3. Creating a Database">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="tutorial-start.html" title="Chapter 1. Getting Started">Up</a></td><th width="60%" align="center">Chapter 1. Getting Started</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="tutorial-sql.html" title="Chapter 2. The SQL Language">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="TUTORIAL-ACCESSDB"><div class="titlepage"><div><div><h2 class="title" style="clear: both">1.4. Accessing a Database</h2></div></div></div><a id="id-1.4.3.5.2" class="indexterm"></a><p>

  3.     Once you have created a database, you can access it by:

  4. 

  5.     </p><div class="itemizedlist"><ul class="itemizedlist compact" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><p>

  6.        Running the <span class="productname">PostgreSQL</span> interactive

  7.        terminal program, called <span class="application"><em class="firstterm">psql</em></span>, which allows you

  8.        to interactively enter, edit, and execute

  9.        <acronym class="acronym">SQL</acronym> commands.

  10.       </p></li><li class="listitem" style="list-style-type: disc"><p>

  11.        Using an existing graphical frontend tool like

  12.        <span class="application">pgAdmin</span> or an office suite with

  13.        <acronym class="acronym">ODBC</acronym> or <acronym class="acronym">JDBC</acronym> support to create and manipulate a

  14.        database.  These possibilities are not covered in this

  15.        tutorial.

  16.       </p></li><li class="listitem" style="list-style-type: disc"><p>

  17.        Writing a custom application, using one of the several

  18.        available language bindings.  These possibilities are discussed

  19.        further in <a class="xref" href="client-interfaces.html" title="Part IV. Client Interfaces">Part IV</a>.

  20.       </p></li></ul></div><p>

  21. 

  22.     You probably want to start up <code class="command">psql</code> to try

  23.     the examples in this tutorial.  It can be activated for the

  24.     <code class="literal">mydb</code> database by typing the command:

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

  26. <code class="prompt">$</code> <strong class="userinput"><code>psql mydb</code></strong>

  27. </pre><p>

  28.     If you do not supply the database name then it will default to your

  29.     user account name.  You already discovered this scheme in the

  30.     previous section using <code class="command">createdb</code>.

  31.    </p><p>

  32.     In <code class="command">psql</code>, you will be greeted with the following

  33.     message:

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

  35. psql (12.4)

  36. Type "help" for help.

  37. 

  38. mydb=&gt;

  39. </pre><p>

  40.     <a id="id-1.4.3.5.4.3" class="indexterm"></a>

  41.     The last line could also be:

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

  43. mydb=#

  44. </pre><p>

  45.     That would mean you are a database superuser, which is most likely

  46.     the case if you installed the <span class="productname">PostgreSQL</span> instance

  47.     yourself.  Being a superuser means that you are not subject to

  48.     access controls.  For the purposes of this tutorial that is not

  49.     important.

  50.    </p><p>

  51.     If you encounter problems starting <code class="command">psql</code>

  52.     then go back to the previous section.  The diagnostics of

  53.     <code class="command">createdb</code> and <code class="command">psql</code> are

  54.     similar, and if the former worked the latter should work as well.

  55.    </p><p>

  56.     The last line printed out by <code class="command">psql</code> is the

  57.     prompt, and it indicates that <code class="command">psql</code> is listening

  58.     to you and that you can type <acronym class="acronym">SQL</acronym> queries into a

  59.     work space maintained by <code class="command">psql</code>.  Try out these

  60.     commands:

  61.     <a id="id-1.4.3.5.6.5" class="indexterm"></a>

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

  63. <code class="prompt">mydb=&gt;</code> <strong class="userinput"><code>SELECT version();</code></strong>

  64.                                          version

  65. ------------------------------------------------------------------------------------------

  66.  PostgreSQL 12.4 on x86_64-pc-linux-gnu, compiled by gcc (Debian 4.9.2-10) 4.9.2, 64-bit

  67. (1 row)

  68. 

  69. <code class="prompt">mydb=&gt;</code> <strong class="userinput"><code>SELECT current_date;</code></strong>

  70.     date

  71. ------------

  72.  2016-01-07

  73. (1 row)

  74. 

  75. <code class="prompt">mydb=&gt;</code> <strong class="userinput"><code>SELECT 2 + 2;</code></strong>

  76.  ?column?

  77. ----------

  78.         4

  79. (1 row)

  80. </pre><p>

  81.    </p><p>

  82.     The <code class="command">psql</code> program has a number of internal

  83.     commands that are not SQL commands.  They begin with the backslash

  84.     character, <span class="quote">“<span class="quote"><code class="literal">\</code></span>”</span>.

  85.     For example,

  86.     you can get help on the syntax of various

  87.     <span class="productname">PostgreSQL</span> <acronym class="acronym">SQL</acronym>

  88.     commands by typing:

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

  90. <code class="prompt">mydb=&gt;</code> <strong class="userinput"><code>\h</code></strong>

  91. </pre><p>

  92.    </p><p>

  93.     To get out of <code class="command">psql</code>, type:

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

  95. <code class="prompt">mydb=&gt;</code> <strong class="userinput"><code>\q</code></strong>

  96. </pre><p>

  97.     and <code class="command">psql</code> will quit and return you to your

  98.     command shell. (For more internal commands, type

  99.     <code class="literal">\?</code> at the <code class="command">psql</code> prompt.)  The

  100.     full capabilities of <code class="command">psql</code> are documented in

  101.     <a class="xref" href="app-psql.html" title="psql"><span class="refentrytitle"><span class="application">psql</span></span></a>.  In this tutorial we will not use these

  102.     features explicitly, but you can use them yourself when it is helpful.

  103.    </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tutorial-createdb.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="tutorial-start.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="tutorial-sql.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">1.3. Creating a Database </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 2. The <acronym class="acronym">SQL</acronym> Language</td></tr></table></div></body></html>
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