Re: IF...THEN...ELSE on INSERT

On Sat, 2001-12-08 at 00:34, Vincent AE Scott wrote:
> What's the fastest / most effecient way todo a test on an insert
> operation and then change the SQL that gets exeuted?
>
> Specifically, i want to check if a row already exists, and then instead
> of inserting the row, just increment a counter for that row.

I usually find this best implemented in a PL/PGSQL function:

CREATE FUNCTION myfunc( TEXT, NUMBER ) RETURNS INT4 AS '
DECLARE
p_1 ALIAS FOR $1;
p_2 ALIAS FOR $2;
curr_val TEXT;
BEGIN
SELECT <something> INTO curr_val FROM mytable
WHERE table_id = p_1;
IF FOUND THEN
UPDATE mytable SET upfield = p_2
WHERE table_id = p_1;
ELSE
INSERT INTO mytable (table_id, upfield)
VALUES( p_1, p_2 );
END IF;
RETURN <whatever>;
END;
' LANGUAGE 'plpgsql';

Hope that helps,
Andrew.
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