ok
Direktori : /opt/alt/postgresql11/usr/share/doc/alt-postgresql11-9.2.24/html/ |
Current File : //opt/alt/postgresql11/usr/share/doc/alt-postgresql11-9.2.24/html/functions-srf.html |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Set Returning Functions</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Functions and Operators" HREF="functions.html"><LINK REL="PREVIOUS" TITLE="Row and Array Comparisons" HREF="functions-comparisons.html"><LINK REL="NEXT" TITLE="System Information Functions" HREF="functions-info.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Row and Array Comparisons" HREF="functions-comparisons.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="functions.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 9. Functions and Operators</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="System Information Functions" HREF="functions-info.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="FUNCTIONS-SRF" >9.24. Set Returning Functions</A ></H1 ><P > 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 <A HREF="functions-srf.html#FUNCTIONS-SRF-SERIES" >Table 9-49</A > and <A HREF="functions-srf.html#FUNCTIONS-SRF-SUBSCRIPTS" >Table 9-50</A >. </P ><DIV CLASS="TABLE" ><A NAME="FUNCTIONS-SRF-SERIES" ></A ><P ><B >Table 9-49. Series Generating Functions</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><THEAD ><TR ><TH >Function</TH ><TH >Argument Type</TH ><TH >Return Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >generate_series(<TT CLASS="PARAMETER" >start</TT >, <TT CLASS="PARAMETER" >stop</TT >)</CODE ></TT ></TD ><TD ><TT CLASS="TYPE" >int</TT > or <TT CLASS="TYPE" >bigint</TT ></TD ><TD ><TT CLASS="TYPE" >setof int</TT > or <TT CLASS="TYPE" >setof bigint</TT > (same as argument type)</TD ><TD > Generate a series of values, from <TT CLASS="PARAMETER" >start</TT > to <TT CLASS="PARAMETER" >stop</TT > with a step size of one </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >generate_series(<TT CLASS="PARAMETER" >start</TT >, <TT CLASS="PARAMETER" >stop</TT >, <TT CLASS="PARAMETER" >step</TT >)</CODE ></TT ></TD ><TD ><TT CLASS="TYPE" >int</TT > or <TT CLASS="TYPE" >bigint</TT ></TD ><TD ><TT CLASS="TYPE" >setof int</TT > or <TT CLASS="TYPE" >setof bigint</TT > (same as argument type)</TD ><TD > Generate a series of values, from <TT CLASS="PARAMETER" >start</TT > to <TT CLASS="PARAMETER" >stop</TT > with a step size of <TT CLASS="PARAMETER" >step</TT > </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >generate_series(<TT CLASS="PARAMETER" >start</TT >, <TT CLASS="PARAMETER" >stop</TT >, <TT CLASS="PARAMETER" >step</TT > <TT CLASS="TYPE" >interval</TT >)</CODE ></TT ></TD ><TD ><TT CLASS="TYPE" >timestamp</TT > or <TT CLASS="TYPE" >timestamp with time zone</TT ></TD ><TD ><TT CLASS="TYPE" >setof timestamp</TT > or <TT CLASS="TYPE" >setof timestamp with time zone</TT > (same as argument type)</TD ><TD > Generate a series of values, from <TT CLASS="PARAMETER" >start</TT > to <TT CLASS="PARAMETER" >stop</TT > with a step size of <TT CLASS="PARAMETER" >step</TT > </TD ></TR ></TBODY ></TABLE ></DIV ><P > When <TT CLASS="PARAMETER" >step</TT > is positive, zero rows are returned if <TT CLASS="PARAMETER" >start</TT > is greater than <TT CLASS="PARAMETER" >stop</TT >. Conversely, when <TT CLASS="PARAMETER" >step</TT > is negative, zero rows are returned if <TT CLASS="PARAMETER" >start</TT > is less than <TT CLASS="PARAMETER" >stop</TT >. Zero rows are also returned for <TT CLASS="LITERAL" >NULL</TT > inputs. It is an error for <TT CLASS="PARAMETER" >step</TT > 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) -- 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" ><A NAME="FUNCTIONS-SRF-SUBSCRIPTS" ></A ><P ><B >Table 9-50. Subscript Generating Functions</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >Function</TH ><TH >Return Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >generate_subscripts(<TT CLASS="PARAMETER" >array anyarray</TT >, <TT CLASS="PARAMETER" >dim int</TT >)</CODE ></TT ></TD ><TD ><TT CLASS="TYPE" >setof int</TT ></TD ><TD > Generate a series comprising the given array's subscripts. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >generate_subscripts(<TT CLASS="PARAMETER" >array anyarray</TT >, <TT CLASS="PARAMETER" >dim int</TT >, <TT CLASS="PARAMETER" >reverse boolean</TT >)</CODE ></TT ></TD ><TD ><TT CLASS="TYPE" >setof int</TT ></TD ><TD > Generate a series comprising the given array's subscripts. When <TT CLASS="PARAMETER" >reverse</TT > is true, the series is returned in reverse order. </TD ></TR ></TBODY ></TABLE ></DIV ><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 for NULL arrays (but valid subscripts are returned for NULL array elements). 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 postgres=# SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]); unnest2 --------- 1 2 3 4 (4 rows)</PRE ><P> </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="functions-comparisons.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="functions-info.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Row and Array Comparisons</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="functions.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >System Information Functions</TD ></TR ></TABLE ></DIV ></BODY ></HTML >