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Support SQL/PSM-compatible CASE statement in plpgsql.

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Pavel Stehule
This commit is contained in:
Tom Lane
2008-05-15 22:39:49 +00:00
parent 0fdb350cae
commit b62f246fb0
11 changed files with 704 additions and 65 deletions
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19
doc/src/sgml/errcodes.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/errcodes.sgml,v 1.23 2008/01/15 01:36:53 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/errcodes.sgml,v 1.24 2008/05/15 22:39:48 tgl Exp $ -->
<appendix id="errcodes-appendix">
<title><productname>PostgreSQL</productname> Error Codes</title>
@ -62,14 +62,14 @@
<tgroup cols="3">
<colspec colnum="1" colname="errorcode">
<colspec colnum="3" colname="constant">
<spanspec namest="errorcode" nameend="constant" spanname="span13">
<colspec colnum="3" colname="condname">
<spanspec namest="errorcode" nameend="condname" spanname="span13">
<thead>
<row>
<entry>Error Code</entry>
<entry>Meaning</entry>
<entry>Constant</entry>
<entry>Condition Name</entry>
</row>
</thead>
@ -292,6 +292,17 @@
</row>
<row>
<entry spanname="span13"><emphasis role="bold">Class 20 &mdash; Case Not Found</></entry>
</row>
<row>
<entry><literal>20000</literal></entry>
<entry>CASE NOT FOUND</entry>
<entry>case_not_found</entry>
</row>
<row>
<entry spanname="span13"><emphasis role="bold">Class 21 &mdash; Cardinality Violation</></entry>
</row>

111
doc/src/sgml/plpgsql.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.129 2008/05/13 22:10:29 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.130 2008/05/15 22:39:49 tgl Exp $ -->
<chapter id="plpgsql">
<title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@ -1581,9 +1581,9 @@ SELECT * FROM getallfoo();
<title>Conditionals</title>
<para>
<literal>IF</> statements let you execute commands based on
certain conditions. <application>PL/pgSQL</> has five forms of
<literal>IF</>:
<command>IF</> and <command>CASE</> statements let you execute
alternative commands based on certain conditions.
<application>PL/pgSQL</> has five forms of <command>IF</>:
<itemizedlist>
<listitem>
<para><literal>IF ... THEN</></>
@ -1601,6 +1601,22 @@ SELECT * FROM getallfoo();
<para><literal>IF ... THEN ... ELSEIF ... THEN ... ELSE</></>
</listitem>
</itemizedlist>
and four forms of <command>CASE</>:
<itemizedlist>
<listitem>
<para><literal>CASE ... WHEN ... THEN ... END CASE</></>
</listitem>
<listitem>
<para><literal>CASE ... WHEN ... THEN ... ELSE ... END CASE</></>
</listitem>
<listitem>
<para><literal>CASE WHEN ... THEN ... END CASE</></>
</listitem>
<listitem>
<para><literal>CASE WHEN ... THEN ... ELSE ... END CASE</></>
</listitem>
</itemizedlist>
</para>
<sect3>
@ -1751,6 +1767,93 @@ END IF;
<literal>ELSEIF</> is an alias for <literal>ELSIF</>.
</para>
</sect3>
<sect3>
<title>Simple <literal>CASE</></title>
<synopsis>
CASE <replaceable>search-expression</replaceable>
WHEN <replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> <optional> ... </optional></optional> THEN
<replaceable>statements</replaceable>
<optional> WHEN <replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> <optional> ... </optional></optional> THEN
<replaceable>statements</replaceable>
... </optional>
<optional> ELSE
<replaceable>statements</replaceable> </optional>
END CASE;
</synopsis>
<para>
The simple form of <command>CASE</> provides conditional execution
based on equality of operands. The <replaceable>search-expression</>
is evaluated (once) and successively compared to each
<replaceable>expression</> in the <literal>WHEN</> clauses.
If a match is found, then the corresponding
<replaceable>statements</replaceable> are executed, and then control
passes to the next statement after <literal>END CASE</>. (Subsequent
<literal>WHEN</> expressions are not evaluated.) If no match is
found, the <literal>ELSE</> <replaceable>statements</replaceable> are
executed; but if <literal>ELSE</> is not present, then a
<literal>CASE_NOT_FOUND</literal> exception is raised.
</para>
<para>
Here is a simple example:
<programlisting>
CASE x
WHEN 1, 2 THEN
msg := 'one or two';
ELSE
msg := 'other value than one or two';
END CASE;
</programlisting>
</para>
</sect3>
<sect3>
<title>Searched <literal>CASE</></title>
<synopsis>
CASE
WHEN <replaceable>boolean-expression</replaceable> THEN
<replaceable>statements</replaceable>
<optional> WHEN <replaceable>boolean-expression</replaceable> THEN
<replaceable>statements</replaceable>
... </optional>
<optional> ELSE
<replaceable>statements</replaceable> </optional>
END CASE;
</synopsis>
<para>
The searched form of <command>CASE</> provides conditional execution
based on truth of boolean expressions. Each <literal>WHEN</> clause's
<replaceable>boolean-expression</replaceable> is evaluated in turn,
until one is found that yields <literal>true</>. Then the
corresponding <replaceable>statements</replaceable> are executed, and
then control passes to the next statement after <literal>END CASE</>.
(Subsequent <literal>WHEN</> expressions are not evaluated.)
If no true result is found, the <literal>ELSE</>
<replaceable>statements</replaceable> are executed;
but if <literal>ELSE</> is not present, then a
<literal>CASE_NOT_FOUND</literal> exception is raised.
</para>
<para>
Here is an example:
<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;
</programlisting>
</para>
</sect3>
</sect2>
<sect2 id="plpgsql-control-structures-loops">