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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Control Structures</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="PL/pgSQL - SQL Procedural Language" HREF="plpgsql.html"><LINK REL="PREVIOUS" TITLE="Basic Statements" HREF="plpgsql-statements.html"><LINK REL="NEXT" TITLE="Cursors" HREF="plpgsql-cursors.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="Basic Statements" HREF="plpgsql-statements.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="plpgsql.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 39. <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > - <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM > Procedural Language</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Cursors" HREF="plpgsql-cursors.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="PLPGSQL-CONTROL-STRUCTURES" >39.6. Control Structures</A ></H1 ><P > Control structures are probably the most useful (and important) part of <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN >. With <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN >'s control structures, you can manipulate <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > data in a very flexible and powerful way. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-STATEMENTS-RETURNING" >39.6.1. Returning From a Function</A ></H2 ><P > There are two commands available that allow you to return data from a function: <TT CLASS="COMMAND" >RETURN</TT > and <TT CLASS="COMMAND" >RETURN NEXT</TT >. </P ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56796" >39.6.1.1. <TT CLASS="COMMAND" >RETURN</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >RETURN <TT CLASS="REPLACEABLE" ><I >expression</I ></TT >;</PRE ><P > <TT CLASS="COMMAND" >RETURN</TT > with an expression terminates the function and returns the value of <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > to the caller. This form is used for <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > functions that do not return a set. </P ><P > When returning a scalar type, any expression can be used. The expression's result will be automatically cast into the function's return type as described for assignments. To return a composite (row) value, you must write a record or row variable as the <TT CLASS="REPLACEABLE" ><I >expression</I ></TT >. </P ><P > If you declared the function with output parameters, write just <TT CLASS="COMMAND" >RETURN</TT > with no expression. The current values of the output parameter variables will be returned. </P ><P > If you declared the function to return <TT CLASS="TYPE" >void</TT >, a <TT CLASS="COMMAND" >RETURN</TT > statement can be used to exit the function early; but do not write an expression following <TT CLASS="COMMAND" >RETURN</TT >. </P ><P > The return value of a function cannot be left undefined. If control reaches the end of the top-level block of the function without hitting a <TT CLASS="COMMAND" >RETURN</TT > statement, a run-time error will occur. This restriction does not apply to functions with output parameters and functions returning <TT CLASS="TYPE" >void</TT >, however. In those cases a <TT CLASS="COMMAND" >RETURN</TT > statement is automatically executed if the top-level block finishes. </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56817" >39.6.1.2. <TT CLASS="COMMAND" >RETURN NEXT</TT > and <TT CLASS="COMMAND" >RETURN QUERY</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >RETURN NEXT <TT CLASS="REPLACEABLE" ><I >expression</I ></TT >; RETURN QUERY <TT CLASS="REPLACEABLE" ><I >query</I ></TT >; RETURN QUERY EXECUTE <TT CLASS="REPLACEABLE" ><I >command-string</I ></TT > [<SPAN CLASS="OPTIONAL" > USING <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" >, ... </SPAN >] </SPAN >];</PRE ><P > When a <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function is declared to return <TT CLASS="LITERAL" >SETOF <TT CLASS="REPLACEABLE" ><I >sometype</I ></TT ></TT >, the procedure to follow is slightly different. In that case, the individual items to return are specified by a sequence of <TT CLASS="COMMAND" >RETURN NEXT</TT > or <TT CLASS="COMMAND" >RETURN QUERY</TT > commands, and then a final <TT CLASS="COMMAND" >RETURN</TT > command with no argument is used to indicate that the function has finished executing. <TT CLASS="COMMAND" >RETURN NEXT</TT > can be used with both scalar and composite data types; with a composite result type, an entire <SPAN CLASS="QUOTE" >"table"</SPAN > of results will be returned. <TT CLASS="COMMAND" >RETURN QUERY</TT > appends the results of executing a query to the function's result set. <TT CLASS="COMMAND" >RETURN NEXT</TT > and <TT CLASS="COMMAND" >RETURN QUERY</TT > can be freely intermixed in a single set-returning function, in which case their results will be concatenated. </P ><P > <TT CLASS="COMMAND" >RETURN NEXT</TT > and <TT CLASS="COMMAND" >RETURN QUERY</TT > do not actually return from the function — they simply append zero or more rows to the function's result set. Execution then continues with the next statement in the <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function. As successive <TT CLASS="COMMAND" >RETURN NEXT</TT > or <TT CLASS="COMMAND" >RETURN QUERY</TT > commands are executed, the result set is built up. A final <TT CLASS="COMMAND" >RETURN</TT >, which should have no argument, causes control to exit the function (or you can just let control reach the end of the function). </P ><P > <TT CLASS="COMMAND" >RETURN QUERY</TT > has a variant <TT CLASS="COMMAND" >RETURN QUERY EXECUTE</TT >, which specifies the query to be executed dynamically. Parameter expressions can be inserted into the computed query string via <TT CLASS="LITERAL" >USING</TT >, in just the same way as in the <TT CLASS="COMMAND" >EXECUTE</TT > command. </P ><P > If you declared the function with output parameters, write just <TT CLASS="COMMAND" >RETURN NEXT</TT > with no expression. On each execution, the current values of the output parameter variable(s) will be saved for eventual return as a row of the result. Note that you must declare the function as returning <TT CLASS="LITERAL" >SETOF record</TT > when there are multiple output parameters, or <TT CLASS="LITERAL" >SETOF <TT CLASS="REPLACEABLE" ><I >sometype</I ></TT ></TT > when there is just one output parameter of type <TT CLASS="REPLACEABLE" ><I >sometype</I ></TT >, in order to create a set-returning function with output parameters. </P ><P > Here is an example of a function using <TT CLASS="COMMAND" >RETURN NEXT</TT >: </P><PRE CLASS="PROGRAMLISTING" >CREATE TABLE foo (fooid INT, foosubid INT, fooname TEXT); INSERT INTO foo VALUES (1, 2, 'three'); INSERT INTO foo VALUES (4, 5, 'six'); CREATE OR REPLACE FUNCTION getAllFoo() RETURNS SETOF foo AS $BODY$ DECLARE r foo%rowtype; BEGIN FOR r IN SELECT * FROM foo WHERE fooid > 0 LOOP -- can do some processing here RETURN NEXT r; -- return current row of SELECT END LOOP; RETURN; END $BODY$ LANGUAGE plpgsql; SELECT * FROM getallfoo();</PRE ><P> </P ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B > The current implementation of <TT CLASS="COMMAND" >RETURN NEXT</TT > and <TT CLASS="COMMAND" >RETURN QUERY</TT > stores the entire result set before returning from the function, as discussed above. That means that if a <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function produces a very large result set, performance might be poor: data will be written to disk to avoid memory exhaustion, but the function itself will not return until the entire result set has been generated. A future version of <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > might allow users to define set-returning functions that do not have this limitation. Currently, the point at which data begins being written to disk is controlled by the <A HREF="runtime-config-resource.html#GUC-WORK-MEM" >work_mem</A > configuration variable. Administrators who have sufficient memory to store larger result sets in memory should consider increasing this parameter. </P ></BLOCKQUOTE ></DIV ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-CONDITIONALS" >39.6.2. Conditionals</A ></H2 ><P > <TT CLASS="COMMAND" >IF</TT > and <TT CLASS="COMMAND" >CASE</TT > statements let you execute alternative commands based on certain conditions. <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > has three forms of <TT CLASS="COMMAND" >IF</TT >: <P ></P ></P><UL ><LI ><P ><TT CLASS="LITERAL" >IF ... THEN</TT ></P ></LI ><LI ><P ><TT CLASS="LITERAL" >IF ... THEN ... ELSE</TT ></P ></LI ><LI ><P ><TT CLASS="LITERAL" >IF ... THEN ... ELSIF ... THEN ... ELSE</TT ></P ></LI ></UL ><P> and two forms of <TT CLASS="COMMAND" >CASE</TT >: <P ></P ></P><UL ><LI ><P ><TT CLASS="LITERAL" >CASE ... WHEN ... THEN ... ELSE ... END CASE</TT ></P ></LI ><LI ><P ><TT CLASS="LITERAL" >CASE WHEN ... THEN ... ELSE ... END CASE</TT ></P ></LI ></UL ><P> </P ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56899" >39.6.2.1. <TT CLASS="LITERAL" >IF-THEN</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >IF <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END IF;</PRE ><P > <TT CLASS="LITERAL" >IF-THEN</TT > statements are the simplest form of <TT CLASS="LITERAL" >IF</TT >. The statements between <TT CLASS="LITERAL" >THEN</TT > and <TT CLASS="LITERAL" >END IF</TT > will be executed if the condition is true. Otherwise, they are skipped. </P ><P > Example: </P><PRE CLASS="PROGRAMLISTING" >IF v_user_id <> 0 THEN UPDATE users SET email = v_email WHERE user_id = v_user_id; END IF;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56912" >39.6.2.2. <TT CLASS="LITERAL" >IF-THEN-ELSE</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >IF <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > ELSE <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END IF;</PRE ><P > <TT CLASS="LITERAL" >IF-THEN-ELSE</TT > statements add to <TT CLASS="LITERAL" >IF-THEN</TT > by letting you specify an alternative set of statements that should be executed if the condition is not true. (Note this includes the case where the condition evaluates to NULL.) </P ><P > Examples: </P><PRE CLASS="PROGRAMLISTING" >IF parentid IS NULL OR parentid = '' THEN RETURN fullname; ELSE RETURN hp_true_filename(parentid) || '/' || fullname; END IF;</PRE ><P> </P><PRE CLASS="PROGRAMLISTING" >IF v_count > 0 THEN INSERT INTO users_count (count) VALUES (v_count); RETURN 't'; ELSE RETURN 'f'; END IF;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56925" >39.6.2.3. <TT CLASS="LITERAL" >IF-THEN-ELSIF</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >IF <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > [<SPAN CLASS="OPTIONAL" > ELSIF <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > [<SPAN CLASS="OPTIONAL" > ELSIF <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > ...</SPAN >]</SPAN >] [<SPAN CLASS="OPTIONAL" > ELSE <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > </SPAN >] END IF;</PRE ><P > Sometimes there are more than just two alternatives. <TT CLASS="LITERAL" >IF-THEN-ELSIF</TT > provides a convenient method of checking several alternatives in turn. The <TT CLASS="LITERAL" >IF</TT > conditions are tested successively until the first one that is true is found. Then the associated statement(s) are executed, after which control passes to the next statement after <TT CLASS="LITERAL" >END IF</TT >. (Any subsequent <TT CLASS="LITERAL" >IF</TT > conditions are <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >not</I ></SPAN > tested.) If none of the <TT CLASS="LITERAL" >IF</TT > conditions is true, then the <TT CLASS="LITERAL" >ELSE</TT > block (if any) is executed. </P ><P > Here is an example: </P><PRE CLASS="PROGRAMLISTING" >IF number = 0 THEN result := 'zero'; ELSIF number > 0 THEN result := 'positive'; ELSIF number < 0 THEN result := 'negative'; ELSE -- hmm, the only other possibility is that number is null result := 'NULL'; END IF;</PRE ><P> </P ><P > The key word <TT CLASS="LITERAL" >ELSIF</TT > can also be spelled <TT CLASS="LITERAL" >ELSEIF</TT >. </P ><P > An alternative way of accomplishing the same task is to nest <TT CLASS="LITERAL" >IF-THEN-ELSE</TT > statements, as in the following example: </P><PRE CLASS="PROGRAMLISTING" >IF demo_row.sex = 'm' THEN pretty_sex := 'man'; ELSE IF demo_row.sex = 'f' THEN pretty_sex := 'woman'; END IF; END IF;</PRE ><P> </P ><P > However, this method requires writing a matching <TT CLASS="LITERAL" >END IF</TT > for each <TT CLASS="LITERAL" >IF</TT >, so it is much more cumbersome than using <TT CLASS="LITERAL" >ELSIF</TT > when there are many alternatives. </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56959" >39.6.2.4. Simple <TT CLASS="LITERAL" >CASE</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >CASE <TT CLASS="REPLACEABLE" ><I >search-expression</I ></TT > WHEN <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" >, <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" > ... </SPAN >]</SPAN >] THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > [<SPAN CLASS="OPTIONAL" > WHEN <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" >, <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" > ... </SPAN >]</SPAN >] THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > ... </SPAN >] [<SPAN CLASS="OPTIONAL" > ELSE <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > </SPAN >] END CASE;</PRE ><P > The simple form of <TT CLASS="COMMAND" >CASE</TT > provides conditional execution based on equality of operands. The <TT CLASS="REPLACEABLE" ><I >search-expression</I ></TT > is evaluated (once) and successively compared to each <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > in the <TT CLASS="LITERAL" >WHEN</TT > clauses. If a match is found, then the corresponding <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > are executed, and then control passes to the next statement after <TT CLASS="LITERAL" >END CASE</TT >. (Subsequent <TT CLASS="LITERAL" >WHEN</TT > expressions are not evaluated.) If no match is found, the <TT CLASS="LITERAL" >ELSE</TT > <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > are executed; but if <TT CLASS="LITERAL" >ELSE</TT > is not present, then a <TT CLASS="LITERAL" >CASE_NOT_FOUND</TT > exception is raised. </P ><P > Here is a simple example: </P><PRE CLASS="PROGRAMLISTING" >CASE x WHEN 1, 2 THEN msg := 'one or two'; ELSE msg := 'other value than one or two'; END CASE;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN56991" >39.6.2.5. Searched <TT CLASS="LITERAL" >CASE</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >CASE WHEN <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > [<SPAN CLASS="OPTIONAL" > WHEN <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > THEN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > ... </SPAN >] [<SPAN CLASS="OPTIONAL" > ELSE <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > </SPAN >] END CASE;</PRE ><P > The searched form of <TT CLASS="COMMAND" >CASE</TT > provides conditional execution based on truth of Boolean expressions. Each <TT CLASS="LITERAL" >WHEN</TT > clause's <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > is evaluated in turn, until one is found that yields <TT CLASS="LITERAL" >true</TT >. Then the corresponding <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > are executed, and then control passes to the next statement after <TT CLASS="LITERAL" >END CASE</TT >. (Subsequent <TT CLASS="LITERAL" >WHEN</TT > expressions are not evaluated.) If no true result is found, the <TT CLASS="LITERAL" >ELSE</TT > <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > are executed; but if <TT CLASS="LITERAL" >ELSE</TT > is not present, then a <TT CLASS="LITERAL" >CASE_NOT_FOUND</TT > exception is raised. </P ><P > Here is an example: </P><PRE CLASS="PROGRAMLISTING" >CASE WHEN x BETWEEN 0 AND 10 THEN msg := 'value is between zero and ten'; WHEN x BETWEEN 11 AND 20 THEN msg := 'value is between eleven and twenty'; END CASE;</PRE ><P> </P ><P > This form of <TT CLASS="COMMAND" >CASE</TT > is entirely equivalent to <TT CLASS="LITERAL" >IF-THEN-ELSIF</TT >, except for the rule that reaching an omitted <TT CLASS="LITERAL" >ELSE</TT > clause results in an error rather than doing nothing. </P ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-CONTROL-STRUCTURES-LOOPS" >39.6.3. Simple Loops</A ></H2 ><P > With the <TT CLASS="LITERAL" >LOOP</TT >, <TT CLASS="LITERAL" >EXIT</TT >, <TT CLASS="LITERAL" >CONTINUE</TT >, <TT CLASS="LITERAL" >WHILE</TT >, <TT CLASS="LITERAL" >FOR</TT >, and <TT CLASS="LITERAL" >FOREACH</TT > statements, you can arrange for your <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function to repeat a series of commands. </P ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN57033" >39.6.3.1. <TT CLASS="LITERAL" >LOOP</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P > <TT CLASS="LITERAL" >LOOP</TT > defines an unconditional loop that is repeated indefinitely until terminated by an <TT CLASS="LITERAL" >EXIT</TT > or <TT CLASS="COMMAND" >RETURN</TT > statement. The optional <TT CLASS="REPLACEABLE" ><I >label</I ></TT > can be used by <TT CLASS="LITERAL" >EXIT</TT > and <TT CLASS="LITERAL" >CONTINUE</TT > statements within nested loops to specify which loop those statements refer to. </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN57049" >39.6.3.2. <TT CLASS="LITERAL" >EXIT</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >EXIT [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >] [<SPAN CLASS="OPTIONAL" > WHEN <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > </SPAN >];</PRE ><P > If no <TT CLASS="REPLACEABLE" ><I >label</I ></TT > is given, the innermost loop is terminated and the statement following <TT CLASS="LITERAL" >END LOOP</TT > is executed next. If <TT CLASS="REPLACEABLE" ><I >label</I ></TT > is given, it must be the label of the current or some outer level of nested loop or block. Then the named loop or block is terminated and control continues with the statement after the loop's/block's corresponding <TT CLASS="LITERAL" >END</TT >. </P ><P > If <TT CLASS="LITERAL" >WHEN</TT > is specified, the loop exit occurs only if <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > is true. Otherwise, control passes to the statement after <TT CLASS="LITERAL" >EXIT</TT >. </P ><P > <TT CLASS="LITERAL" >EXIT</TT > can be used with all types of loops; it is not limited to use with unconditional loops. </P ><P > When used with a <TT CLASS="LITERAL" >BEGIN</TT > block, <TT CLASS="LITERAL" >EXIT</TT > passes control to the next statement after the end of the block. Note that a label must be used for this purpose; an unlabelled <TT CLASS="LITERAL" >EXIT</TT > is never considered to match a <TT CLASS="LITERAL" >BEGIN</TT > block. (This is a change from pre-8.4 releases of <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN >, which would allow an unlabelled <TT CLASS="LITERAL" >EXIT</TT > to match a <TT CLASS="LITERAL" >BEGIN</TT > block.) </P ><P > Examples: </P><PRE CLASS="PROGRAMLISTING" >LOOP -- some computations IF count > 0 THEN EXIT; -- exit loop END IF; END LOOP; LOOP -- some computations EXIT WHEN count > 0; -- same result as previous example END LOOP; <<ablock>> BEGIN -- some computations IF stocks > 100000 THEN EXIT ablock; -- causes exit from the BEGIN block END IF; -- computations here will be skipped when stocks > 100000 END;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN57081" >39.6.3.3. <TT CLASS="LITERAL" >CONTINUE</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >CONTINUE [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >] [<SPAN CLASS="OPTIONAL" > WHEN <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > </SPAN >];</PRE ><P > If no <TT CLASS="REPLACEABLE" ><I >label</I ></TT > is given, the next iteration of the innermost loop is begun. That is, all statements remaining in the loop body are skipped, and control returns to the loop control expression (if any) to determine whether another loop iteration is needed. If <TT CLASS="REPLACEABLE" ><I >label</I ></TT > is present, it specifies the label of the loop whose execution will be continued. </P ><P > If <TT CLASS="LITERAL" >WHEN</TT > is specified, the next iteration of the loop is begun only if <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > is true. Otherwise, control passes to the statement after <TT CLASS="LITERAL" >CONTINUE</TT >. </P ><P > <TT CLASS="LITERAL" >CONTINUE</TT > can be used with all types of loops; it is not limited to use with unconditional loops. </P ><P > Examples: </P><PRE CLASS="PROGRAMLISTING" >LOOP -- some computations EXIT WHEN count > 100; CONTINUE WHEN count < 50; -- some computations for count IN [50 .. 100] END LOOP;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN57103" >39.6.3.4. <TT CLASS="LITERAL" >WHILE</TT ></A ></H3 ><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] WHILE <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P > The <TT CLASS="LITERAL" >WHILE</TT > statement repeats a sequence of statements so long as the <TT CLASS="REPLACEABLE" ><I >boolean-expression</I ></TT > evaluates to true. The expression is checked just before each entry to the loop body. </P ><P > For example: </P><PRE CLASS="PROGRAMLISTING" >WHILE amount_owed > 0 AND gift_certificate_balance > 0 LOOP -- some computations here END LOOP; WHILE NOT done LOOP -- some computations here END LOOP;</PRE ><P> </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="PLPGSQL-INTEGER-FOR" >39.6.3.5. <TT CLASS="LITERAL" >FOR</TT > (Integer Variant)</A ></H3 ><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] FOR <TT CLASS="REPLACEABLE" ><I >name</I ></TT > IN [<SPAN CLASS="OPTIONAL" > REVERSE </SPAN >] <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > .. <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" > BY <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > </SPAN >] LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P > This form of <TT CLASS="LITERAL" >FOR</TT > creates a loop that iterates over a range of integer values. The variable <TT CLASS="REPLACEABLE" ><I >name</I ></TT > is automatically defined as type <TT CLASS="TYPE" >integer</TT > and exists only inside the loop (any existing definition of the variable name is ignored within the loop). The two expressions giving the lower and upper bound of the range are evaluated once when entering the loop. If the <TT CLASS="LITERAL" >BY</TT > clause isn't specified the iteration step is 1, otherwise it's the value specified in the <TT CLASS="LITERAL" >BY</TT > clause, which again is evaluated once on loop entry. If <TT CLASS="LITERAL" >REVERSE</TT > is specified then the step value is subtracted, rather than added, after each iteration. </P ><P > Some examples of integer <TT CLASS="LITERAL" >FOR</TT > loops: </P><PRE CLASS="PROGRAMLISTING" >FOR i IN 1..10 LOOP -- i will take on the values 1,2,3,4,5,6,7,8,9,10 within the loop END LOOP; FOR i IN REVERSE 10..1 LOOP -- i will take on the values 10,9,8,7,6,5,4,3,2,1 within the loop END LOOP; FOR i IN REVERSE 10..1 BY 2 LOOP -- i will take on the values 10,8,6,4,2 within the loop END LOOP;</PRE ><P> </P ><P > If the lower bound is greater than the upper bound (or less than, in the <TT CLASS="LITERAL" >REVERSE</TT > case), the loop body is not executed at all. No error is raised. </P ><P > If a <TT CLASS="REPLACEABLE" ><I >label</I ></TT > is attached to the <TT CLASS="LITERAL" >FOR</TT > loop then the integer loop variable can be referenced with a qualified name, using that <TT CLASS="REPLACEABLE" ><I >label</I ></TT >. </P ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-RECORDS-ITERATING" >39.6.4. Looping Through Query Results</A ></H2 ><P > Using a different type of <TT CLASS="LITERAL" >FOR</TT > loop, you can iterate through the results of a query and manipulate that data accordingly. The syntax is: </P><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] FOR <TT CLASS="REPLACEABLE" ><I >target</I ></TT > IN <TT CLASS="REPLACEABLE" ><I >query</I ></TT > LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P> The <TT CLASS="REPLACEABLE" ><I >target</I ></TT > is a record variable, row variable, or comma-separated list of scalar variables. The <TT CLASS="REPLACEABLE" ><I >target</I ></TT > is successively assigned each row resulting from the <TT CLASS="REPLACEABLE" ><I >query</I ></TT > and the loop body is executed for each row. Here is an example: </P><PRE CLASS="PROGRAMLISTING" >CREATE FUNCTION cs_refresh_mviews() RETURNS integer AS $$ DECLARE mviews RECORD; BEGIN RAISE NOTICE 'Refreshing materialized views...'; FOR mviews IN SELECT * FROM cs_materialized_views ORDER BY sort_key LOOP -- Now "mviews" has one record from cs_materialized_views RAISE NOTICE 'Refreshing materialized view %s ...', quote_ident(mviews.mv_name); EXECUTE 'TRUNCATE TABLE ' || quote_ident(mviews.mv_name); EXECUTE 'INSERT INTO ' || quote_ident(mviews.mv_name) || ' ' || mviews.mv_query; END LOOP; RAISE NOTICE 'Done refreshing materialized views.'; RETURN 1; END; $$ LANGUAGE plpgsql;</PRE ><P> If the loop is terminated by an <TT CLASS="LITERAL" >EXIT</TT > statement, the last assigned row value is still accessible after the loop. </P ><P > The <TT CLASS="REPLACEABLE" ><I >query</I ></TT > used in this type of <TT CLASS="LITERAL" >FOR</TT > statement can be any SQL command that returns rows to the caller: <TT CLASS="COMMAND" >SELECT</TT > is the most common case, but you can also use <TT CLASS="COMMAND" >INSERT</TT >, <TT CLASS="COMMAND" >UPDATE</TT >, or <TT CLASS="COMMAND" >DELETE</TT > with a <TT CLASS="LITERAL" >RETURNING</TT > clause. Some utility commands such as <TT CLASS="COMMAND" >EXPLAIN</TT > will work too. </P ><P > <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > variables are substituted into the query text, and the query plan is cached for possible re-use, as discussed in detail in <A HREF="plpgsql-implementation.html#PLPGSQL-VAR-SUBST" >Section 39.10.1</A > and <A HREF="plpgsql-implementation.html#PLPGSQL-PLAN-CACHING" >Section 39.10.2</A >. </P ><P > The <TT CLASS="LITERAL" >FOR-IN-EXECUTE</TT > statement is another way to iterate over rows: </P><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] FOR <TT CLASS="REPLACEABLE" ><I >target</I ></TT > IN EXECUTE <TT CLASS="REPLACEABLE" ><I >text_expression</I ></TT > [<SPAN CLASS="OPTIONAL" > USING <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > [<SPAN CLASS="OPTIONAL" >, ... </SPAN >] </SPAN >] LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P> This is like the previous form, except that the source query is specified as a string expression, which is evaluated and replanned on each entry to the <TT CLASS="LITERAL" >FOR</TT > loop. This allows the programmer to choose the speed of a preplanned query or the flexibility of a dynamic query, just as with a plain <TT CLASS="COMMAND" >EXECUTE</TT > statement. As with <TT CLASS="COMMAND" >EXECUTE</TT >, parameter values can be inserted into the dynamic command via <TT CLASS="LITERAL" >USING</TT >. </P ><P > Another way to specify the query whose results should be iterated through is to declare it as a cursor. This is described in <A HREF="plpgsql-cursors.html#PLPGSQL-CURSOR-FOR-LOOP" >Section 39.7.4</A >. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-FOREACH-ARRAY" >39.6.5. Looping Through Arrays</A ></H2 ><P > The <TT CLASS="LITERAL" >FOREACH</TT > loop is much like a <TT CLASS="LITERAL" >FOR</TT > loop, but instead of iterating through the rows returned by a SQL query, it iterates through the elements of an array value. (In general, <TT CLASS="LITERAL" >FOREACH</TT > is meant for looping through components of a composite-valued expression; variants for looping through composites besides arrays may be added in future.) The <TT CLASS="LITERAL" >FOREACH</TT > statement to loop over an array is: </P><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] FOREACH <TT CLASS="REPLACEABLE" ><I >target</I ></TT > [<SPAN CLASS="OPTIONAL" > SLICE <TT CLASS="REPLACEABLE" ><I >number</I ></TT > </SPAN >] IN ARRAY <TT CLASS="REPLACEABLE" ><I >expression</I ></TT > LOOP <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > END LOOP [<SPAN CLASS="OPTIONAL" > <TT CLASS="REPLACEABLE" ><I >label</I ></TT > </SPAN >];</PRE ><P> </P ><P > Without <TT CLASS="LITERAL" >SLICE</TT >, or if <TT CLASS="LITERAL" >SLICE 0</TT > is specified, the loop iterates through individual elements of the array produced by evaluating the <TT CLASS="REPLACEABLE" ><I >expression</I ></TT >. The <TT CLASS="REPLACEABLE" ><I >target</I ></TT > variable is assigned each element value in sequence, and the loop body is executed for each element. Here is an example of looping through the elements of an integer array: </P><PRE CLASS="PROGRAMLISTING" >CREATE FUNCTION sum(int[]) RETURNS int8 AS $$ DECLARE s int8 := 0; x int; BEGIN FOREACH x IN ARRAY $1 LOOP s := s + x; END LOOP; RETURN s; END; $$ LANGUAGE plpgsql;</PRE ><P> The elements are visited in storage order, regardless of the number of array dimensions. Although the <TT CLASS="REPLACEABLE" ><I >target</I ></TT > is usually just a single variable, it can be a list of variables when looping through an array of composite values (records). In that case, for each array element, the variables are assigned from successive columns of the composite value. </P ><P > With a positive <TT CLASS="LITERAL" >SLICE</TT > value, <TT CLASS="LITERAL" >FOREACH</TT > iterates through slices of the array rather than single elements. The <TT CLASS="LITERAL" >SLICE</TT > value must be an integer constant not larger than the number of dimensions of the array. The <TT CLASS="REPLACEABLE" ><I >target</I ></TT > variable must be an array, and it receives successive slices of the array value, where each slice is of the number of dimensions specified by <TT CLASS="LITERAL" >SLICE</TT >. Here is an example of iterating through one-dimensional slices: </P><PRE CLASS="PROGRAMLISTING" >CREATE FUNCTION scan_rows(int[]) RETURNS void AS $$ DECLARE x int[]; BEGIN FOREACH x SLICE 1 IN ARRAY $1 LOOP RAISE NOTICE 'row = %', x; END LOOP; END; $$ LANGUAGE plpgsql; SELECT scan_rows(ARRAY[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]); NOTICE: row = {1,2,3} NOTICE: row = {4,5,6} NOTICE: row = {7,8,9} NOTICE: row = {10,11,12}</PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PLPGSQL-ERROR-TRAPPING" >39.6.6. Trapping Errors</A ></H2 ><P > By default, any error occurring in a <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function aborts execution of the function, and indeed of the surrounding transaction as well. You can trap errors and recover from them by using a <TT CLASS="COMMAND" >BEGIN</TT > block with an <TT CLASS="LITERAL" >EXCEPTION</TT > clause. The syntax is an extension of the normal syntax for a <TT CLASS="COMMAND" >BEGIN</TT > block: </P><PRE CLASS="SYNOPSIS" >[<SPAN CLASS="OPTIONAL" > <<<TT CLASS="REPLACEABLE" ><I >label</I ></TT >>> </SPAN >] [<SPAN CLASS="OPTIONAL" > DECLARE <TT CLASS="REPLACEABLE" ><I >declarations</I ></TT > </SPAN >] BEGIN <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > EXCEPTION WHEN <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > [<SPAN CLASS="OPTIONAL" > OR <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > ... </SPAN >] THEN <TT CLASS="REPLACEABLE" ><I >handler_statements</I ></TT > [<SPAN CLASS="OPTIONAL" > WHEN <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > [<SPAN CLASS="OPTIONAL" > OR <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > ... </SPAN >] THEN <TT CLASS="REPLACEABLE" ><I >handler_statements</I ></TT > ... </SPAN >] END;</PRE ><P> </P ><P > If no error occurs, this form of block simply executes all the <TT CLASS="REPLACEABLE" ><I >statements</I ></TT >, and then control passes to the next statement after <TT CLASS="LITERAL" >END</TT >. But if an error occurs within the <TT CLASS="REPLACEABLE" ><I >statements</I ></TT >, further processing of the <TT CLASS="REPLACEABLE" ><I >statements</I ></TT > is abandoned, and control passes to the <TT CLASS="LITERAL" >EXCEPTION</TT > list. The list is searched for the first <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > matching the error that occurred. If a match is found, the corresponding <TT CLASS="REPLACEABLE" ><I >handler_statements</I ></TT > are executed, and then control passes to the next statement after <TT CLASS="LITERAL" >END</TT >. If no match is found, the error propagates out as though the <TT CLASS="LITERAL" >EXCEPTION</TT > clause were not there at all: the error can be caught by an enclosing block with <TT CLASS="LITERAL" >EXCEPTION</TT >, or if there is none it aborts processing of the function. </P ><P > The <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > names can be any of those shown in <A HREF="errcodes-appendix.html" >Appendix A</A >. A category name matches any error within its category. The special condition name <TT CLASS="LITERAL" >OTHERS</TT > matches every error type except <TT CLASS="LITERAL" >QUERY_CANCELED</TT >. (It is possible, but often unwise, to trap <TT CLASS="LITERAL" >QUERY_CANCELED</TT > by name.) Condition names are not case-sensitive. Also, an error condition can be specified by <TT CLASS="LITERAL" >SQLSTATE</TT > code; for example these are equivalent: </P><PRE CLASS="PROGRAMLISTING" >WHEN division_by_zero THEN ... WHEN SQLSTATE '22012' THEN ...</PRE ><P> </P ><P > If a new error occurs within the selected <TT CLASS="REPLACEABLE" ><I >handler_statements</I ></TT >, it cannot be caught by this <TT CLASS="LITERAL" >EXCEPTION</TT > clause, but is propagated out. A surrounding <TT CLASS="LITERAL" >EXCEPTION</TT > clause could catch it. </P ><P > When an error is caught by an <TT CLASS="LITERAL" >EXCEPTION</TT > clause, the local variables of the <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN > function remain as they were when the error occurred, but all changes to persistent database state within the block are rolled back. As an example, consider this fragment: </P><PRE CLASS="PROGRAMLISTING" >INSERT INTO mytab(firstname, lastname) VALUES('Tom', 'Jones'); BEGIN UPDATE mytab SET firstname = 'Joe' WHERE lastname = 'Jones'; x := x + 1; y := x / 0; EXCEPTION WHEN division_by_zero THEN RAISE NOTICE 'caught division_by_zero'; RETURN x; END;</PRE ><P> When control reaches the assignment to <TT CLASS="LITERAL" >y</TT >, it will fail with a <TT CLASS="LITERAL" >division_by_zero</TT > error. This will be caught by the <TT CLASS="LITERAL" >EXCEPTION</TT > clause. The value returned in the <TT CLASS="COMMAND" >RETURN</TT > statement will be the incremented value of <TT CLASS="LITERAL" >x</TT >, but the effects of the <TT CLASS="COMMAND" >UPDATE</TT > command will have been rolled back. The <TT CLASS="COMMAND" >INSERT</TT > command preceding the block is not rolled back, however, so the end result is that the database contains <TT CLASS="LITERAL" >Tom Jones</TT > not <TT CLASS="LITERAL" >Joe Jones</TT >. </P ><DIV CLASS="TIP" ><BLOCKQUOTE CLASS="TIP" ><P ><B >Tip: </B > A block containing an <TT CLASS="LITERAL" >EXCEPTION</TT > clause is significantly more expensive to enter and exit than a block without one. Therefore, don't use <TT CLASS="LITERAL" >EXCEPTION</TT > without need. </P ></BLOCKQUOTE ></DIV ><DIV CLASS="EXAMPLE" ><A NAME="PLPGSQL-UPSERT-EXAMPLE" ></A ><P ><B >Example 39-2. Exceptions with <TT CLASS="COMMAND" >UPDATE</TT >/<TT CLASS="COMMAND" >INSERT</TT ></B ></P ><P > This example uses exception handling to perform either <TT CLASS="COMMAND" >UPDATE</TT > or <TT CLASS="COMMAND" >INSERT</TT >, as appropriate: </P><PRE CLASS="PROGRAMLISTING" >CREATE TABLE db (a INT PRIMARY KEY, b TEXT); CREATE FUNCTION merge_db(key INT, data TEXT) RETURNS VOID AS $$ BEGIN LOOP -- first try to update the key UPDATE db SET b = data WHERE a = key; IF found THEN RETURN; END IF; -- not there, so try to insert the key -- if someone else inserts the same key concurrently, -- we could get a unique-key failure BEGIN INSERT INTO db(a,b) VALUES (key, data); RETURN; EXCEPTION WHEN unique_violation THEN -- Do nothing, and loop to try the UPDATE again. END; END LOOP; END; $$ LANGUAGE plpgsql; SELECT merge_db(1, 'david'); SELECT merge_db(1, 'dennis');</PRE ><P> This coding assumes the <TT CLASS="LITERAL" >unique_violation</TT > error is caused by the <TT CLASS="COMMAND" >INSERT</TT >, and not by, say, an <TT CLASS="COMMAND" >INSERT</TT > in a trigger function on the table. It might also misbehave if there is more than one unique index on the table, since it will retry the operation regardless of which index caused the error. More safety could be had by using the features discussed next to check that the trapped error was the one expected. </P ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="PLPGSQL-EXCEPTION-DIAGNOSTICS" >39.6.6.1. Obtaining information about an error</A ></H3 ><P > Exception handlers frequently need to identify the specific error that occurred. There are two ways to get information about the current exception in <SPAN CLASS="APPLICATION" >PL/pgSQL</SPAN >: special variables and the <TT CLASS="COMMAND" >GET STACKED DIAGNOSTICS</TT > command. </P ><P > Within an exception handler, the special variable <TT CLASS="VARNAME" >SQLSTATE</TT > contains the error code that corresponds to the exception that was raised (refer to <A HREF="errcodes-appendix.html#ERRCODES-TABLE" >Table A-1</A > for a list of possible error codes). The special variable <TT CLASS="VARNAME" >SQLERRM</TT > contains the error message associated with the exception. These variables are undefined outside exception handlers. </P ><P > Within an exception handler, one may also retrieve information about the current exception by using the <TT CLASS="COMMAND" >GET STACKED DIAGNOSTICS</TT > command, which has the form: </P><PRE CLASS="SYNOPSIS" >GET STACKED DIAGNOSTICS <TT CLASS="REPLACEABLE" ><I >variable</I ></TT > = <TT CLASS="REPLACEABLE" ><I >item</I ></TT > [<SPAN CLASS="OPTIONAL" > , ... </SPAN >];</PRE ><P> Each <TT CLASS="REPLACEABLE" ><I >item</I ></TT > is a key word identifying a status value to be assigned to the specified variable (which should be of the right data type to receive it). The currently available status items are shown in <A HREF="plpgsql-control-structures.html#PLPGSQL-EXCEPTION-DIAGNOSTICS-VALUES" >Table 39-1</A >. </P ><DIV CLASS="TABLE" ><A NAME="PLPGSQL-EXCEPTION-DIAGNOSTICS-VALUES" ></A ><P ><B >Table 39-1. Error diagnostics values</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >RETURNED_SQLSTATE</TT ></TD ><TD >text</TD ><TD >the SQLSTATE error code of the exception</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >MESSAGE_TEXT</TT ></TD ><TD >text</TD ><TD >the text of the exception's primary message</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >PG_EXCEPTION_DETAIL</TT ></TD ><TD >text</TD ><TD >the text of the exception's detail message, if any</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >PG_EXCEPTION_HINT</TT ></TD ><TD >text</TD ><TD >the text of the exception's hint message, if any</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >PG_EXCEPTION_CONTEXT</TT ></TD ><TD >text</TD ><TD >line(s) of text describing the call stack</TD ></TR ></TBODY ></TABLE ></DIV ><P > If the exception did not set a value for an item, an empty string will be returned. </P ><P > Here is an example: </P><PRE CLASS="PROGRAMLISTING" >DECLARE text_var1 text; text_var2 text; text_var3 text; BEGIN -- some processing which might cause an exception ... EXCEPTION WHEN OTHERS THEN GET STACKED DIAGNOSTICS text_var1 = MESSAGE_TEXT, text_var2 = PG_EXCEPTION_DETAIL, text_var3 = PG_EXCEPTION_HINT; END;</PRE ><P> </P ></DIV ></DIV ></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="plpgsql-statements.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="plpgsql-cursors.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Basic Statements</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="plpgsql.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Cursors</TD ></TR ></TABLE ></DIV ></BODY ></HTML >