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by Martin Pitt
Import upstream version 9.3~beta1 |
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>Structure of PL/pgSQL</TITLE |
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1.1.11
by Martin Pitt
Import upstream version 9.3.12 |
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TITLE="PostgreSQL 9.3.12 Documentation" |
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1
by Martin Pitt
Import upstream version 9.3~beta1 |
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TITLE="PL/pgSQL - SQL Procedural Language" |
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TITLE="Overview" |
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1.1.11
by Martin Pitt
Import upstream version 9.3.12 |
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CONTENT="2016-03-28T20:28:06"></HEAD |
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by Martin Pitt
Import upstream version 9.3~beta1 |
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1.1.11
by Martin Pitt
Import upstream version 9.3.12 |
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>PostgreSQL 9.3.12 Documentation</A |
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by Martin Pitt
Import upstream version 9.3~beta1 |
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></TR |
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><TR |
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><TD |
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WIDTH="10%" |
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ALIGN="left" |
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VALIGN="top" |
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><A |
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TITLE="Overview" |
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HREF="plpgsql-overview.html" |
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ACCESSKEY="P" |
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>Prev</A |
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></TD |
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><TD |
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WIDTH="10%" |
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ALIGN="left" |
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VALIGN="top" |
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HREF="plpgsql.html" |
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>Up</A |
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><TD |
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WIDTH="60%" |
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ALIGN="center" |
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VALIGN="bottom" |
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>Chapter 40. <SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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> - <ACRONYM |
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CLASS="ACRONYM" |
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>SQL</ACRONYM |
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> Procedural Language</TD |
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><TD |
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WIDTH="20%" |
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ALIGN="right" |
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VALIGN="top" |
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><A |
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TITLE="Declarations" |
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HREF="plpgsql-declarations.html" |
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ACCESSKEY="N" |
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>Next</A |
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></TD |
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></TR |
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></TABLE |
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><HR |
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ALIGN="LEFT" |
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WIDTH="100%"></DIV |
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CLASS="SECT1" |
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><H1 |
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><A |
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NAME="PLPGSQL-STRUCTURE" |
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>40.2. Structure of <SPAN |
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>PL/pgSQL</SPAN |
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></A |
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></H1 |
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><P |
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> <SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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> is a block-structured language.
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The complete text of a function definition must be a |
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<I |
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CLASS="FIRSTTERM" |
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>block</I |
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>. A block is defined as:
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</P><PRE |
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CLASS="SYNOPSIS" |
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>[<SPAN |
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CLASS="OPTIONAL" |
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> <<<TT |
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CLASS="REPLACEABLE" |
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><I |
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>label</I |
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></TT |
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>>> </SPAN |
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>]
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[<SPAN |
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CLASS="OPTIONAL" |
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> DECLARE
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<TT |
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CLASS="REPLACEABLE" |
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><I |
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>declarations</I |
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></TT |
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> </SPAN |
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>]
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BEGIN |
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<TT |
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CLASS="REPLACEABLE" |
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><I |
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>statements</I |
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></TT |
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>
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END [<SPAN |
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CLASS="OPTIONAL" |
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> <TT |
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CLASS="REPLACEABLE" |
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><I |
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>label</I |
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></TT |
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> </SPAN |
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>];</PRE |
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><P> |
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</P |
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><P |
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> Each declaration and each statement within a block is terminated
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by a semicolon. A block that appears within another block must |
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have a semicolon after <TT |
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CLASS="LITERAL" |
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>END</TT |
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>, as shown above;
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however the final <TT |
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CLASS="LITERAL" |
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>END</TT |
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> that
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concludes a function body does not require a semicolon. |
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</P |
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><DIV |
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CLASS="TIP" |
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><BLOCKQUOTE |
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CLASS="TIP" |
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><P |
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><B |
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>Tip: </B |
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> A common mistake is to write a semicolon immediately after
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<TT |
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CLASS="LITERAL" |
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>BEGIN</TT |
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>. This is incorrect and will result in a syntax error.
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</P |
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></BLOCKQUOTE |
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></DIV |
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><P |
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> A <TT |
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CLASS="REPLACEABLE" |
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><I |
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>label</I |
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></TT |
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> is only needed if you want to
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identify the block for use |
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in an <TT |
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CLASS="LITERAL" |
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>EXIT</TT |
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> statement, or to qualify the names of the
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variables declared in the block. If a label is given after |
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<TT |
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CLASS="LITERAL" |
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>END</TT |
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>, it must match the label at the block's beginning.
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</P |
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><P |
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> All key words are case-insensitive.
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Identifiers are implicitly converted to lower case |
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unless double-quoted, just as they are in ordinary SQL commands. |
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</P |
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><P |
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> Comments work the same way in <SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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> code as in
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ordinary SQL. A double dash (<TT |
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CLASS="LITERAL" |
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>--</TT |
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>) starts a comment
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that extends to the end of the line. A <TT |
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CLASS="LITERAL" |
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>/*</TT |
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> starts a
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block comment that extends to the matching occurrence of |
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<TT |
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CLASS="LITERAL" |
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>*/</TT |
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>. Block comments nest.
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</P |
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><P |
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> Any statement in the statement section of a block
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can be a <I |
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CLASS="FIRSTTERM" |
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>subblock</I |
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>. Subblocks can be used for
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logical grouping or to localize variables to a small group |
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of statements. Variables declared in a subblock mask any |
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similarly-named variables of outer blocks for the duration |
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of the subblock; but you can access the outer variables anyway |
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if you qualify their names with their block's label. For example: |
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</P><PRE |
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CLASS="PROGRAMLISTING" |
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>CREATE FUNCTION somefunc() RETURNS integer AS $$
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<< outerblock >> |
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DECLARE |
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quantity integer := 30; |
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BEGIN |
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RAISE NOTICE 'Quantity here is %', quantity; -- Prints 30 |
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quantity := 50; |
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-- |
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-- Create a subblock |
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-- |
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DECLARE |
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quantity integer := 80; |
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BEGIN |
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RAISE NOTICE 'Quantity here is %', quantity; -- Prints 80 |
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RAISE NOTICE 'Outer quantity here is %', outerblock.quantity; -- Prints 50 |
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END; |
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RAISE NOTICE 'Quantity here is %', quantity; -- Prints 50 |
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RETURN quantity; |
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END; |
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$$ LANGUAGE plpgsql;</PRE |
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><P> |
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</P |
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><DIV |
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CLASS="NOTE" |
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><BLOCKQUOTE |
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CLASS="NOTE" |
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><P |
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><B |
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>Note: </B |
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> There is actually a hidden <SPAN |
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CLASS="QUOTE" |
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>"outer block"</SPAN |
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> surrounding the body
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of any <SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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> function. This block provides the
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declarations of the function's parameters (if any), as well as some |
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special variables such as <TT |
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CLASS="LITERAL" |
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>FOUND</TT |
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> (see
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<A |
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HREF="plpgsql-statements.html#PLPGSQL-STATEMENTS-DIAGNOSTICS" |
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>Section 40.5.5</A |
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>). The outer block is
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labeled with the function's name, meaning that parameters and special |
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variables can be qualified with the function's name. |
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</P |
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></BLOCKQUOTE |
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></DIV |
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><P |
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> It is important not to confuse the use of
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<TT |
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CLASS="COMMAND" |
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>BEGIN</TT |
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>/<TT |
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CLASS="COMMAND" |
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>END</TT |
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> for grouping statements in
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<SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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> with the similarly-named SQL commands
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for transaction |
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control. <SPAN |
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CLASS="APPLICATION" |
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>PL/pgSQL</SPAN |
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>'s <TT |
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CLASS="COMMAND" |
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>BEGIN</TT |
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>/<TT |
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CLASS="COMMAND" |
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>END</TT |
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>
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are only for grouping; they do not start or end a transaction. |
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Functions and trigger procedures are always executed within a transaction |
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established by an outer query — they cannot start or commit that
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transaction, since there would be no context for them to execute in. |
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However, a block containing an <TT |
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CLASS="LITERAL" |
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>EXCEPTION</TT |
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> clause effectively
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forms a subtransaction that can be rolled back without affecting the |
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outer transaction. For more about that see <A |
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HREF="plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING" |
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>Section 40.6.6</A |
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>.
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</P |
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WIDTH="33%" |
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ALIGN="left" |
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VALIGN="top" |
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HREF="plpgsql-overview.html" |
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>Prev</A |
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VALIGN="top" |
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HREF="index.html" |
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>Home</A |
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WIDTH="33%" |
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ALIGN="right" |
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HREF="plpgsql-declarations.html" |
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>Next</A |
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><TR |
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><TD |
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WIDTH="33%" |
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ALIGN="left" |
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VALIGN="top" |
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>Overview</TD |
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><TD |
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WIDTH="34%" |
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ALIGN="center" |
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VALIGN="top" |
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HREF="plpgsql.html" |
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ACCESSKEY="U" |
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>Up</A |
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></TD |
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><TD |
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WIDTH="33%" |
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ALIGN="right" |
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VALIGN="top" |
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>Declarations</TD |
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