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<!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>42.2. Structure of PL/pgSQL</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="plpgsql-overview.html" title="42.1. Overview" /><link rel="next" href="plpgsql-declarations.html" title="42.3. Declarations" /></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">42.2. Structure of <span xmlns="http://www.w3.org/1999/xhtml" class="application">PL/pgSQL</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-overview.html" title="42.1. Overview">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 42. PL/pgSQL - SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 42. <span xmlns="http://www.w3.org/1999/xhtml" class="application">PL/pgSQL</span> - <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">SQL</acronym> Procedural Language</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="plpgsql-declarations.html" title="42.3. Declarations">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PLPGSQL-STRUCTURE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">42.2. Structure of <span class="application">PL/pgSQL</span></h2></div></div></div><p>
   Functions written in <span class="application">PL/pgSQL</span> are defined
   to the server by executing <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a> commands.
   Such a command would normally look like, say,
</p><pre class="programlisting">
CREATE FUNCTION somefunc(integer, text) RETURNS integer
AS '<em class="replaceable"><code>function body text</code></em>'
LANGUAGE plpgsql;
</pre><p>
   The function body is simply a string literal so far as <code class="command">CREATE
   FUNCTION</code> is concerned.  It is often helpful to use dollar quoting
   (see <a class="xref" href="sql-syntax-lexical.html#SQL-SYNTAX-DOLLAR-QUOTING" title="4.1.2.4. Dollar-Quoted String Constants">Section 4.1.2.4</a>) to write the function
   body, rather than the normal single quote syntax.  Without dollar quoting,
   any single quotes or backslashes in the function body must be escaped by
   doubling them.  Almost all the examples in this chapter use dollar-quoted
   literals for their function bodies.
  </p><p>
   <span class="application">PL/pgSQL</span> is a block-structured language.
   The complete text of a function body must be a
   <em class="firstterm">block</em>. A block is defined as:

</p><pre class="synopsis">
[<span class="optional"> &lt;&lt;<em class="replaceable"><code>label</code></em>&gt;&gt; </span>]
[<span class="optional"> DECLARE
    <em class="replaceable"><code>declarations</code></em> </span>]
BEGIN
    <em class="replaceable"><code>statements</code></em>
END [<span class="optional"> <em class="replaceable"><code>label</code></em> </span>];
</pre><p>
    </p><p>
     Each declaration and each statement within a block is terminated
     by a semicolon.  A block that appears within another block must
     have a semicolon after <code class="literal">END</code>, as shown above;
     however the final <code class="literal">END</code> that
     concludes a function body does not require a semicolon.
    </p><div class="tip"><h3 class="title">Tip</h3><p>
      A common mistake is to write a semicolon immediately after
      <code class="literal">BEGIN</code>.  This is incorrect and will result in a syntax error.
     </p></div><p>
     A <em class="replaceable"><code>label</code></em> is only needed if you want to
     identify the block for use
     in an <code class="literal">EXIT</code> statement, or to qualify the names of the
     variables declared in the block.  If a label is given after
     <code class="literal">END</code>, it must match the label at the block's beginning.
    </p><p>
     All key words are case-insensitive.
     Identifiers are implicitly converted to lower case
     unless double-quoted, just as they are in ordinary SQL commands.
    </p><p>
     Comments work the same way in <span class="application">PL/pgSQL</span> code as in
     ordinary SQL.  A double dash (<code class="literal">--</code>) starts a comment
     that extends to the end of the line. A <code class="literal">/*</code> starts a
     block comment that extends to the matching occurrence of
     <code class="literal">*/</code>.  Block comments nest.
    </p><p>
     Any statement in the statement section of a block
     can be a <em class="firstterm">subblock</em>.  Subblocks can be used for
     logical grouping or to localize variables to a small group
     of statements.  Variables declared in a subblock mask any
     similarly-named variables of outer blocks for the duration
     of the subblock; but you can access the outer variables anyway
     if you qualify their names with their block's label. For example:
</p><pre class="programlisting">
CREATE FUNCTION somefunc() RETURNS integer AS $$
&lt;&lt; outerblock &gt;&gt;
DECLARE
    quantity integer := 30;
BEGIN
    RAISE NOTICE 'Quantity here is %', quantity;  -- Prints 30
    quantity := 50;
    --
    -- Create a subblock
    --
    DECLARE
        quantity integer := 80;
    BEGIN
        RAISE NOTICE 'Quantity here is %', quantity;  -- Prints 80
        RAISE NOTICE 'Outer quantity here is %', outerblock.quantity;  -- Prints 50
    END;

    RAISE NOTICE 'Quantity here is %', quantity;  -- Prints 50

    RETURN quantity;
END;
$$ LANGUAGE plpgsql;
</pre><p>
    </p><div class="note"><h3 class="title">Note</h3><p>
      There is actually a hidden <span class="quote">“<span class="quote">outer block</span>”</span> surrounding the body
      of any <span class="application">PL/pgSQL</span> function.  This block provides the
      declarations of the function's parameters (if any), as well as some
      special variables such as <code class="literal">FOUND</code> (see
      <a class="xref" href="plpgsql-statements.html#PLPGSQL-STATEMENTS-DIAGNOSTICS" title="42.5.5. Obtaining the Result Status">Section 42.5.5</a>).  The outer block is
      labeled with the function's name, meaning that parameters and special
      variables can be qualified with the function's name.
     </p></div><p>
     It is important not to confuse the use of
     <code class="command">BEGIN</code>/<code class="command">END</code> for grouping statements in
     <span class="application">PL/pgSQL</span> with the similarly-named SQL commands
     for transaction
     control.  <span class="application">PL/pgSQL</span>'s <code class="command">BEGIN</code>/<code class="command">END</code>
     are only for grouping; they do not start or end a transaction.
     See <a class="xref" href="plpgsql-transactions.html" title="42.8. Transaction Management">Section 42.8</a> for information on managing
     transactions in <span class="application">PL/pgSQL</span>.
     Also, a block containing an <code class="literal">EXCEPTION</code> clause effectively
     forms a subtransaction that can be rolled back without affecting the
     outer transaction.  For more about that see <a class="xref" href="plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING" title="42.6.8. Trapping Errors">Section 42.6.8</a>.
    </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpgsql-overview.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpgsql-declarations.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">42.1. Overview </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 42.3. Declarations</td></tr></table></div></body></html>