<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Array Functions and Operators</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 8.4.12 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Functions and Operators" HREF="functions.html"><LINK REL="PREVIOUS" TITLE="Conditional Expressions" HREF="functions-conditional.html"><LINK REL="NEXT" TITLE="Aggregate Functions" HREF="functions-aggregate.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="2012-05-31T23:30:11"></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" >PostgreSQL 8.4.12 Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="functions-conditional.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="functions.html" >Fast Backward</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 9. Functions and Operators</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="functions.html" >Fast Forward</A ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="functions-aggregate.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="FUNCTIONS-ARRAY" >9.17. Array Functions and Operators</A ></H1 ><P > <A HREF="functions-array.html#ARRAY-OPERATORS-TABLE" >Table 9-40</A > shows the operators available for array types. </P ><DIV CLASS="TABLE" ><A NAME="ARRAY-OPERATORS-TABLE" ></A ><P ><B >Table 9-40. Array Operators</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><THEAD ><TR ><TH >Operator</TH ><TH >Description</TH ><TH >Example</TH ><TH >Result</TH ></TR ></THEAD ><TBODY ><TR ><TD > <TT CLASS="LITERAL" >=</TT > </TD ><TD >equal</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" ><></TT > </TD ><TD >not equal</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,2,3] <> ARRAY[1,2,4]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" ><</TT > </TD ><TD >less than</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,2,3] < ARRAY[1,2,4]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >></TT > </TD ><TD >greater than</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,4,3] > ARRAY[1,2,4]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" ><=</TT > </TD ><TD >less than or equal</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,2,3] <= ARRAY[1,2,3]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >>=</TT > </TD ><TD >greater than or equal</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,4,3] >= ARRAY[1,4,3]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >@></TT > </TD ><TD >contains</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,4,3] @> ARRAY[3,1]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" ><@</TT > </TD ><TD >is contained by</TD ><TD ><TT CLASS="LITERAL" >ARRAY[2,7] <@ ARRAY[1,7,4,2,6]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >&&</TT > </TD ><TD >overlap (have elements in common)</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,4,3] && ARRAY[2,1]</TT ></TD ><TD ><TT CLASS="LITERAL" >t</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >||</TT > </TD ><TD >array-to-array concatenation</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,2,3] || ARRAY[4,5,6]</TT ></TD ><TD ><TT CLASS="LITERAL" >{1,2,3,4,5,6}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >||</TT > </TD ><TD >array-to-array concatenation</TD ><TD ><TT CLASS="LITERAL" >ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]</TT ></TD ><TD ><TT CLASS="LITERAL" >{{1,2,3},{4,5,6},{7,8,9}}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >||</TT > </TD ><TD >element-to-array concatenation</TD ><TD ><TT CLASS="LITERAL" >3 || ARRAY[4,5,6]</TT ></TD ><TD ><TT CLASS="LITERAL" >{3,4,5,6}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" >||</TT > </TD ><TD >array-to-element concatenation</TD ><TD ><TT CLASS="LITERAL" >ARRAY[4,5,6] || 7</TT ></TD ><TD ><TT CLASS="LITERAL" >{4,5,6,7}</TT ></TD ></TR ></TBODY ></TABLE ></DIV ><P > Array comparisons compare the array contents element-by-element, using the default B-Tree comparison function for the element data type. In multidimensional arrays the elements are visited in row-major order (last subscript varies most rapidly). If the contents of two arrays are equal but the dimensionality is different, the first difference in the dimensionality information determines the sort order. (This is a change from versions of <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > prior to 8.2: older versions would claim that two arrays with the same contents were equal, even if the number of dimensions or subscript ranges were different.) </P ><P > See <A HREF="arrays.html" >Section 8.14</A > for more details about array operator behavior. </P ><P > <A HREF="functions-array.html#ARRAY-FUNCTIONS-TABLE" >Table 9-41</A > shows the functions available for use with array types. See <A HREF="arrays.html" >Section 8.14</A > for more information and examples of the use of these functions. </P ><A NAME="AEN15452" ></A ><A NAME="AEN15454" ></A ><A NAME="AEN15456" ></A ><A NAME="AEN15458" ></A ><A NAME="AEN15460" ></A ><A NAME="AEN15462" ></A ><A NAME="AEN15464" ></A ><A NAME="AEN15466" ></A ><A NAME="AEN15468" ></A ><A NAME="AEN15470" ></A ><A NAME="AEN15472" ></A ><A NAME="AEN15474" ></A ><DIV CLASS="TABLE" ><A NAME="ARRAY-FUNCTIONS-TABLE" ></A ><P ><B >Table 9-41. Array Functions</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><COL><THEAD ><TR ><TH >Function</TH ><TH >Return Type</TH ><TH >Description</TH ><TH >Example</TH ><TH >Result</TH ></TR ></THEAD ><TBODY ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_append</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >anyelement</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >anyarray</TT ></TD ><TD >append an element to the end of an array</TD ><TD ><TT CLASS="LITERAL" >array_append(ARRAY[1,2], 3)</TT ></TD ><TD ><TT CLASS="LITERAL" >{1,2,3}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_cat</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >anyarray</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >anyarray</TT ></TD ><TD >concatenate two arrays</TD ><TD ><TT CLASS="LITERAL" >array_cat(ARRAY[1,2,3], ARRAY[4,5])</TT ></TD ><TD ><TT CLASS="LITERAL" >{1,2,3,4,5}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_ndims</CODE >(<TT CLASS="TYPE" >anyarray</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >int</TT ></TD ><TD >returns the number of dimensions of the array</TD ><TD ><TT CLASS="LITERAL" >array_ndims(ARRAY[[1,2,3], [4,5,6]])</TT ></TD ><TD ><TT CLASS="LITERAL" >2</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_dims</CODE >(<TT CLASS="TYPE" >anyarray</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD >returns a text representation of array's dimensions</TD ><TD ><TT CLASS="LITERAL" >array_dims(ARRAY[[1,2,3], [4,5,6]])</TT ></TD ><TD ><TT CLASS="LITERAL" >[1:2][1:3]</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_fill</CODE >(<TT CLASS="TYPE" >anyelement</TT >, <TT CLASS="TYPE" >int[]</TT >, [<SPAN CLASS="OPTIONAL" >, <TT CLASS="TYPE" >int[]</TT ></SPAN >]) </TT > </TD ><TD ><TT CLASS="TYPE" >anyarray</TT ></TD ><TD >returns an array initialized with supplied value and dimensions, optionally with lower bounds other than 1</TD ><TD ><TT CLASS="LITERAL" >array_fill(7, ARRAY[3], ARRAY[2])</TT ></TD ><TD ><TT CLASS="LITERAL" >[2:4]={7,7,7}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_length</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >int</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >int</TT ></TD ><TD >returns the length of the requested array dimension</TD ><TD ><TT CLASS="LITERAL" >array_length(array[1,2,3], 1)</TT ></TD ><TD ><TT CLASS="LITERAL" >3</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_lower</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >int</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >int</TT ></TD ><TD >returns lower bound of the requested array dimension</TD ><TD ><TT CLASS="LITERAL" >array_lower('[0:2]={1,2,3}'::int[], 1)</TT ></TD ><TD ><TT CLASS="LITERAL" >0</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_prepend</CODE >(<TT CLASS="TYPE" >anyelement</TT >, <TT CLASS="TYPE" >anyarray</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >anyarray</TT ></TD ><TD >append an element to the beginning of an array</TD ><TD ><TT CLASS="LITERAL" >array_prepend(1, ARRAY[2,3])</TT ></TD ><TD ><TT CLASS="LITERAL" >{1,2,3}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_to_string</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >text</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD >concatenates array elements using supplied delimiter</TD ><TD ><TT CLASS="LITERAL" >array_to_string(ARRAY[1, 2, 3], '~^~')</TT ></TD ><TD ><TT CLASS="LITERAL" >1~^~2~^~3</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >array_upper</CODE >(<TT CLASS="TYPE" >anyarray</TT >, <TT CLASS="TYPE" >int</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >int</TT ></TD ><TD >returns upper bound of the requested array dimension</TD ><TD ><TT CLASS="LITERAL" >array_upper(ARRAY[1,2,3,4], 1)</TT ></TD ><TD ><TT CLASS="LITERAL" >4</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >string_to_array</CODE >(<TT CLASS="TYPE" >text</TT >, <TT CLASS="TYPE" >text</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >text[]</TT ></TD ><TD >splits string into array elements using supplied delimiter</TD ><TD ><TT CLASS="LITERAL" >string_to_array('xx~^~yy~^~zz', '~^~')</TT ></TD ><TD ><TT CLASS="LITERAL" >{xx,yy,zz}</TT ></TD ></TR ><TR ><TD > <TT CLASS="LITERAL" > <CODE CLASS="FUNCTION" >unnest</CODE >(<TT CLASS="TYPE" >anyarray</TT >) </TT > </TD ><TD ><TT CLASS="TYPE" >setof anyelement</TT ></TD ><TD >expand an array to a set of rows</TD ><TD ><TT CLASS="LITERAL" >unnest(ARRAY[1,2])</TT ></TD ><TD ><TT CLASS="LITERAL" >1</TT ><P ><TT CLASS="LITERAL" >2</TT ></P > (2 rows)</TD ></TR ></TBODY ></TABLE ></DIV ><P > See also <A HREF="functions-aggregate.html" >Section 9.18</A > about the aggregate function <CODE CLASS="FUNCTION" >array_agg</CODE > for use with arrays. </P ></DIV ><DIV 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