The following code snippet are picked from PostgreSQL documentation :
http://www.postgresql.org/docs/current/static/plpgsql-declarations.html
CREATE FUNCTION extended_sales(p_itemno int) RETURNS TABLE(quantity int, total
numeric) AS $$
BEGIN
RETURN QUERY SELECT quantity, quantity * price FROM sales WHERE itemno =
p_itemno;
END;
$$ LANGUAGE plpgsql;
I would like modify the following function behavior slightly :
(1) Only return TABLE(quantity int, total numeric), if there is at least one
row meet condition WHERE itemno = p_itemno
(2) If not, create the row, and return TABLE(quantity int, total numeric)
The only way I can think of is :
The only way I can think of to achieve (1) is :
LOOP
SELECT quantity, quantity * price FROM sales WHERE itemno = p_itemno;
-- Fall into creation code block.
EXIT WHEN NOT FOUND;
RETURN QUERY SELECT quantity, quantity * price FROM sales WHERE itemno
= p_itemno;
END LOOP;
But that will be two duplicated SELECT statement. Inefficient, right?
Thanks and Regards
Yan Cheng CHEOK
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