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Documentation for generate_series() functions committed a few days ago.

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Joe Conway 2004-02-05 22:54:36 +00:00
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doc/src/sgml/func.sgml
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$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.185 2003/12/26 21:30:48 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.186 2004/02/05 22:54:36 joe Exp $
PostgreSQL documentation
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</sect2>
</sect1>
<sect1 id="functions-srf">
<title>Set Returning Functions</title>
<indexterm zone="functions-srf">
<primary>set returning functions</primary>
<secondary>functions</secondary>
</indexterm>
<para>
This section describes functions that possibly return more than one row.
Currently the only functions in this class are series generating functions,
as detailed in <xref linkend="functions-srf-series">.
</para>
<table id="functions-srf-series">
<title>Series Generating Functions</title>
<tgroup cols="4">
<thead>
<row>
<entry>Function</entry>
<entry>Argument Type</entry>
<entry>Return Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal><function>generate_series</function>(<parameter>start</parameter>, <parameter>stop</parameter>)</literal></entry>
<entry><type>int</type> or <type>bigint</type></entry>
<entry><type>setof int</type> or <type>setof bigint</type> (same as argument type)</entry>
<entry>
Generate a series of values, from <parameter>start</parameter> to <parameter>stop</parameter>
with a step size of one.
</entry>
</row>
<row>
<entry><literal><function>generate_series</function>(<parameter>start</parameter>, <parameter>stop</parameter>, <parameter>step</parameter>)</literal></entry>
<entry><type>int</type> or <type>bigint</type></entry>
<entry><type>setof int</type> or <type>setof bigint</type> (same as argument type)</entry>
<entry>
Generate a series of values, from <parameter>start</parameter> to <parameter>stop</parameter>
with a step size of <parameter>step</parameter>.
</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
When <parameter>step</parameter> is positive, zero rows are returned if
<parameter>start</parameter> is greater than <parameter>stop</parameter>.
Conversely, when <parameter>step</parameter> is negative, zero rows are
returned if <parameter>start</parameter> is less than <parameter>stop</parameter>.
Zero rows are also returned for <literal>NULL</literal> inputs. It is an error
for <parameter>step</parameter> to be zero. Some examples follow:
<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 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)
</programlisting>
</para>
</sect1>
</chapter>
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