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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 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 15.5 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 /></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 9.64. Series Generating Functions">Table 9.64</a> and
<a class="xref" href="functions-srf.html#FUNCTIONS-SRF-SUBSCRIPTS" title="Table 9.65. Subscript Generating Functions">Table 9.65</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 9.64. 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 9.65. 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>
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