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diff --git a/doc/src/sgml/html/plpgsql-structure.html b/doc/src/sgml/html/plpgsql-structure.html new file mode 100644 index 0000000..1a0fefb --- /dev/null +++ b/doc/src/sgml/html/plpgsql-structure.html @@ -0,0 +1,108 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!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>43.2. 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 Vsnapshot" /><link rel="prev" href="plpgsql-overview.html" title="43.1. Overview" /><link rel="next" href="plpgsql-declarations.html" title="43.3. Declarations" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">43.2. Structure of <span class="application">PL/pgSQL</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-overview.html" title="43.1. Overview">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 43. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plpgsql-declarations.html" title="43.3. Declarations">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPGSQL-STRUCTURE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">43.2. 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"> <<<em class="replaceable"><code>label</code></em>>> </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 $$ +<< outerblock >> +DECLARE + quantity integer := 30; +BEGIN + RAISE NOTICE 'Quantity here is %', quantity; -- Prints 30 + quantity := 50; + -- + -- Create a subblock + -- + DECLARE + quantity integer := 80; + BEGIN + RAISE NOTICE 'Quantity here is %', quantity; -- Prints 80 + RAISE NOTICE 'Outer quantity here is %', outerblock.quantity; -- Prints 50 + END; + + RAISE NOTICE 'Quantity here is %', quantity; -- Prints 50 + + RETURN quantity; +END; +$$ 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="43.5.5. Obtaining the Result Status">Section 43.5.5</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="43.8. Transaction Management">Section 43.8</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="43.6.8. Trapping Errors">Section 43.6.8</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" title="43.1. Overview">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpgsql-declarations.html" title="43.3. Declarations">Next</a></td></tr><tr><td width="40%" align="left" valign="top">43.1. Overview </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 43.3. Declarations</td></tr></table></div></body></html>
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