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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:15:05 +0000
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Adding upstream version 14.5.upstream/14.5upstream
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+<?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>9.25. Set Returning Functions</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="functions-comparisons.html" title="9.24. Row and Array Comparisons" /><link rel="next" href="functions-info.html" title="9.26. System Information Functions and Operators" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.25. Set Returning Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-comparisons.html" title="9.24. Row and Array Comparisons">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 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-info.html" title="9.26. System Information Functions and Operators">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-SRF"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.25. Set Returning Functions</h2></div></div></div><a id="id-1.5.8.31.2" class="indexterm"></a><p>
+ This section describes functions that possibly return more than one row.
+ The most widely used functions in this class are series generating
+ functions, as detailed in <a class="xref" href="functions-srf.html#FUNCTIONS-SRF-SERIES" title="Table 9.63. Series Generating Functions">Table 9.63</a> and
+ <a class="xref" href="functions-srf.html#FUNCTIONS-SRF-SUBSCRIPTS" title="Table 9.64. Subscript Generating Functions">Table 9.64</a>. Other, more specialized
+ set-returning functions are described elsewhere in this manual.
+ See <a class="xref" href="queries-table-expressions.html#QUERIES-TABLEFUNCTIONS" title="7.2.1.4. Table Functions">Section 7.2.1.4</a> for ways to combine multiple
+ set-returning functions.
+ </p><div class="table" id="FUNCTIONS-SRF-SERIES"><p class="title"><strong>Table 9.63. Series Generating Functions</strong></p><div class="table-contents"><table class="table" summary="Series Generating Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
+ Function
+ </p>
+ <p>
+ Description
+ </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
+ <a id="id-1.5.8.31.4.2.2.1.1.1.1" class="indexterm"></a>
+ <code class="function">generate_series</code> ( <em class="parameter"><code>start</code></em> <code class="type">integer</code>, <em class="parameter"><code>stop</code></em> <code class="type">integer</code> [<span class="optional">, <em class="parameter"><code>step</code></em> <code class="type">integer</code> </span>] )
+ → <code class="returnvalue">setof integer</code>
+ </p>
+ <p class="func_signature">
+ <code class="function">generate_series</code> ( <em class="parameter"><code>start</code></em> <code class="type">bigint</code>, <em class="parameter"><code>stop</code></em> <code class="type">bigint</code> [<span class="optional">, <em class="parameter"><code>step</code></em> <code class="type">bigint</code> </span>] )
+ → <code class="returnvalue">setof bigint</code>
+ </p>
+ <p class="func_signature">
+ <code class="function">generate_series</code> ( <em class="parameter"><code>start</code></em> <code class="type">numeric</code>, <em class="parameter"><code>stop</code></em> <code class="type">numeric</code> [<span class="optional">, <em class="parameter"><code>step</code></em> <code class="type">numeric</code> </span>] )
+ → <code class="returnvalue">setof numeric</code>
+ </p>
+ <p>
+ Generates a series of values from <em class="parameter"><code>start</code></em>
+ to <em class="parameter"><code>stop</code></em>, with a step size
+ of <em class="parameter"><code>step</code></em>. <em class="parameter"><code>step</code></em>
+ defaults to 1.
+ </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
+ <code class="function">generate_series</code> ( <em class="parameter"><code>start</code></em> <code class="type">timestamp</code>, <em class="parameter"><code>stop</code></em> <code class="type">timestamp</code>, <em class="parameter"><code>step</code></em> <code class="type">interval</code> )
+ → <code class="returnvalue">setof timestamp</code>
+ </p>
+ <p class="func_signature">
+ <code class="function">generate_series</code> ( <em class="parameter"><code>start</code></em> <code class="type">timestamp with time zone</code>, <em class="parameter"><code>stop</code></em> <code class="type">timestamp with time zone</code>, <em class="parameter"><code>step</code></em> <code class="type">interval</code> )
+ → <code class="returnvalue">setof timestamp with time zone</code>
+ </p>
+ <p>
+ Generates a series of values from <em class="parameter"><code>start</code></em>
+ to <em class="parameter"><code>stop</code></em>, with a step size
+ of <em class="parameter"><code>step</code></em>.
+ </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
+ When <em class="parameter"><code>step</code></em> is positive, zero rows are returned if
+ <em class="parameter"><code>start</code></em> is greater than <em class="parameter"><code>stop</code></em>.
+ Conversely, when <em class="parameter"><code>step</code></em> is negative, zero rows are
+ returned if <em class="parameter"><code>start</code></em> is less than <em class="parameter"><code>stop</code></em>.
+ Zero rows are also returned if any input is <code class="literal">NULL</code>.
+ It is an error
+ for <em class="parameter"><code>step</code></em> to be zero. Some examples follow:
+</p><pre class="programlisting">
+SELECT * FROM generate_series(2,4);
+ generate_series
+-----------------
+ 2
+ 3
+ 4
+(3 rows)
+
+SELECT * FROM generate_series(5,1,-2);
+ generate_series
+-----------------
+ 5
+ 3
+ 1
+(3 rows)
+
+SELECT * FROM generate_series(4,3);
+ generate_series
+-----------------
+(0 rows)
+
+SELECT generate_series(1.1, 4, 1.3);
+ generate_series
+-----------------
+ 1.1
+ 2.4
+ 3.7
+(3 rows)
+
+-- this example relies on the date-plus-integer operator:
+SELECT current_date + s.a AS dates FROM generate_series(0,14,7) AS s(a);
+ dates
+------------
+ 2004-02-05
+ 2004-02-12
+ 2004-02-19
+(3 rows)
+
+SELECT * FROM generate_series('2008-03-01 00:00'::timestamp,
+ '2008-03-04 12:00', '10 hours');
+ generate_series
+---------------------
+ 2008-03-01 00:00:00
+ 2008-03-01 10:00:00
+ 2008-03-01 20:00:00
+ 2008-03-02 06:00:00
+ 2008-03-02 16:00:00
+ 2008-03-03 02:00:00
+ 2008-03-03 12:00:00
+ 2008-03-03 22:00:00
+ 2008-03-04 08:00:00
+(9 rows)
+</pre><p>
+ </p><div class="table" id="FUNCTIONS-SRF-SUBSCRIPTS"><p class="title"><strong>Table 9.64. Subscript Generating Functions</strong></p><div class="table-contents"><table class="table" summary="Subscript Generating Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
+ Function
+ </p>
+ <p>
+ Description
+ </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
+ <a id="id-1.5.8.31.6.2.2.1.1.1.1" class="indexterm"></a>
+ <code class="function">generate_subscripts</code> ( <em class="parameter"><code>array</code></em> <code class="type">anyarray</code>, <em class="parameter"><code>dim</code></em> <code class="type">integer</code> )
+ → <code class="returnvalue">setof integer</code>
+ </p>
+ <p>
+ Generates a series comprising the valid subscripts of
+ the <em class="parameter"><code>dim</code></em>'th dimension of the given array.
+ </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
+ <code class="function">generate_subscripts</code> ( <em class="parameter"><code>array</code></em> <code class="type">anyarray</code>, <em class="parameter"><code>dim</code></em> <code class="type">integer</code>, <em class="parameter"><code>reverse</code></em> <code class="type">boolean</code> )
+ → <code class="returnvalue">setof integer</code>
+ </p>
+ <p>
+ Generates a series comprising the valid subscripts of
+ the <em class="parameter"><code>dim</code></em>'th dimension of the given array.
+ When <em class="parameter"><code>reverse</code></em> is true, returns the series in
+ reverse order.
+ </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
+ <code class="function">generate_subscripts</code> is a convenience function that generates
+ the set of valid subscripts for the specified dimension of the given
+ array.
+ Zero rows are returned for arrays that do not have the requested dimension,
+ or if any input is <code class="literal">NULL</code>.
+ Some examples follow:
+</p><pre class="programlisting">
+-- basic usage:
+SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s;
+ s
+---
+ 1
+ 2
+ 3
+ 4
+(4 rows)
+
+-- presenting an array, the subscript and the subscripted
+-- value requires a subquery:
+SELECT * FROM arrays;
+ a
+--------------------
+ {-1,-2}
+ {100,200,300}
+(2 rows)
+
+SELECT a AS array, s AS subscript, a[s] AS value
+FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo;
+ array | subscript | value
+---------------+-----------+-------
+ {-1,-2} | 1 | -1
+ {-1,-2} | 2 | -2
+ {100,200,300} | 1 | 100
+ {100,200,300} | 2 | 200
+ {100,200,300} | 3 | 300
+(5 rows)
+
+-- unnest a 2D array:
+CREATE OR REPLACE FUNCTION unnest2(anyarray)
+RETURNS SETOF anyelement AS $$
+select $1[i][j]
+ from generate_subscripts($1,1) g1(i),
+ generate_subscripts($1,2) g2(j);
+$$ LANGUAGE sql IMMUTABLE;
+CREATE FUNCTION
+SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
+ unnest2
+---------
+ 1
+ 2
+ 3
+ 4
+(4 rows)
+</pre><p>
+ </p><a id="id-1.5.8.31.8" class="indexterm"></a><p>
+ When a function in the <code class="literal">FROM</code> clause is suffixed
+ by <code class="literal">WITH ORDINALITY</code>, a <code class="type">bigint</code> column is
+ appended to the function's output column(s), which starts from 1 and
+ increments by 1 for each row of the function's output.
+ This is most useful in the case of set returning
+ functions such as <code class="function">unnest()</code>.
+
+</p><pre class="programlisting">
+-- set returning function WITH ORDINALITY:
+SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
+ ls | n
+-----------------+----
+ pg_serial | 1
+ pg_twophase | 2
+ postmaster.opts | 3
+ pg_notify | 4
+ postgresql.conf | 5
+ pg_tblspc | 6
+ logfile | 7
+ base | 8
+ postmaster.pid | 9
+ pg_ident.conf | 10
+ global | 11
+ pg_xact | 12
+ pg_snapshots | 13
+ pg_multixact | 14
+ PG_VERSION | 15
+ pg_wal | 16
+ pg_hba.conf | 17
+ pg_stat_tmp | 18
+ pg_subtrans | 19
+(19 rows)
+</pre><p>
+ </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-comparisons.html" title="9.24. Row and Array Comparisons">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="functions-info.html" title="9.26. System Information Functions and Operators">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.24. Row and Array Comparisons </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 9.26. System Information Functions and Operators</td></tr></table></div></body></html> \ No newline at end of file
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