Functions written in PL/pgSQL are defined to the server by executing CREATE FUNCTION commands. Such a command would normally look like, say,
CREATE FUNCTION somefunc(integer, text) RETURNS integer AS '
function body text' LANGUAGE plpgsql;
The function body is simply a string literal so far as
CREATE FUNCTION is concerned. It is
often helpful to use dollar quoting (see Section 184.108.40.206)
to write the function body, rather than the normal single quote
syntax. Without dollar quoting, any single quotes or backslashes in
the function body must be escaped by doubling them. Almost all the
examples in this chapter use dollar-quoted literals for their
PL/pgSQL is a block-structured language. The complete text of a function body must be a block. A block is defined as:
label>> ] [ DECLARE
Each declaration and each statement within a block is terminated
by a semicolon. A block that appears within another block must have
a semicolon after
END, as shown above;
however the final
END that concludes a
function body does not require a semicolon.
A common mistake is to write a semicolon immediately after
BEGIN. This is incorrect and will
result in a syntax error.
label is only needed
if you want to identify the block for use in an
EXIT statement, or to qualify the names of the
variables declared in the block. If a label is given after
END, it must match the label at the
All key words are case-insensitive. Identifiers are implicitly converted to lower case unless double-quoted, just as they are in ordinary SQL commands.
Comments work the same way in PL/pgSQL code as in ordinary SQL. A double
--) starts a comment that
extends to the end of the line. A
starts a block comment that extends to the matching occurrence of
*/. Block comments nest.
Any statement in the statement section of a block can be a subblock. Subblocks can be used for logical grouping or to localize variables to a small group of statements. Variables declared in a subblock mask any similarly-named variables of outer blocks for the duration of the subblock; but you can access the outer variables anyway if you qualify their names with their block's label. For example:
CREATE FUNCTION somefunc() RETURNS integer AS $$ << outerblock >> DECLARE quantity integer := 30; BEGIN RAISE NOTICE 'Quantity here is %', quantity; -- Prints 30 quantity := 50; -- -- Create a subblock -- DECLARE quantity integer := 80; BEGIN RAISE NOTICE 'Quantity here is %', quantity; -- Prints 80 RAISE NOTICE 'Outer quantity here is %', outerblock.quantity; -- Prints 50 END; RAISE NOTICE 'Quantity here is %', quantity; -- Prints 50 RETURN quantity; END; $$ LANGUAGE plpgsql;
There is actually a hidden “outer block” surrounding the body of any
PL/pgSQL function. This block
provides the declarations of the function's parameters (if any), as
well as some special variables such as
FOUND (see Section 42.5.5).
The outer block is labeled with the function's name, meaning that
parameters and special variables can be qualified with the
It is important not to confuse the use of
grouping statements in PL/pgSQL
with the similarly-named SQL commands for transaction control.
END are only
for grouping; they do not start or end a transaction. Functions and
trigger procedures are always executed within a transaction
established by an outer query — they cannot start or commit that
transaction, since there would be no context for them to execute
in. However, a block containing an
EXCEPTION clause effectively forms a
subtransaction that can be rolled back without affecting the outer
transaction. For more about that see Section 42.6.6.
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