Can I make a plpgsql function return an integer without using a variable?
Yes you can. There are a number of ways.
1) RETURN (SELECT ...)
CREATE OR REPLACE FUNCTION get(_param_id integer)
RETURNS integer AS
$func$
BEGIN
RETURN (SELECT col1 FROM TABLE WHERE id = _param_id);
END
$func$ LANGUAGE plpgsql;
2) Use an OUT
or INOUT
parameter
CREATE OR REPLACE FUNCTION get(_param_id integer, OUT _col1 integer)
-- RETURNS integer -- "RETURNS integer" is optional noise in this case
AS
$func$
BEGIN
SELECT INTO _col1 col1 FROM TABLE WHERE id = _param_id;
-- also valid, but discouraged:
-- _col1 := col1 FROM TABLE WHERE id = _param_id;
END
$func$ LANGUAGE plpgsql;
More in the manual here.
3) (Ab)use IN
parameter
Since Postgres 9.0 you can also use input parameters as variables. The release notes for 9.0:
An input parameter now acts like a local variable initialized to the passed-in value.
CREATE OR REPLACE FUNCTION get(_param_id integer)
RETURNS integer AS
$func$
BEGIN
SELECT INTO _param1 col1 FROM TABLE WHERE id = _param1;
RETURN _param1;
-- Also possible, but discouraged:
-- $1 := col1 FROM TABLE WHERE id = $1;
-- RETURN $1;
END
$func$ LANGUAGE plpgsql;
With the last ones you do use a variable implicitly, but you don't have to DECLARE
it explicitly (as requested).
4) Use a DEFAULT
value with an INOUT
parameter
This is a bit of a special case. The function body can be empty.
CREATE OR REPLACE FUNCTION get(_param_id integer, INOUT _col1 integer = 123)
RETURNS integer AS
$func$
BEGIN
-- You can assign some (other) value to _col1:
-- SELECT INTO _col1 col1 FROM TABLE WHERE id = _param_id;
-- If you don't, the DEFAULT 123 will be returned.
END
$func$ LANGUAGE plpgsql;
INOUT _col1 integer = 123
is short notation for INOUT _col1 integer DEFAULT 123
. More:
- The forgotten assignment operator "=" and the commonplace ":="
5) Use a plain SQL function instead
CREATE OR REPLACE FUNCTION get(_param_id integer)
RETURNS integer AS
$func$
SELECT col1 FROM TABLE WHERE id = _param_id;
-- use positional reference $1 instead of param name in Postgres 9.1 or older
$func$ LANGUAGE sql;