How to SELECT a PROCEDURE in Firebird 2.5

Question

I\'m using Firebird Embedded v2.5. How to use procedures in query (SELECT) ?

My procedure:

SET TERM ^ ;
CREAT         


        

Answer 1

FN_TEST is an executable procedure: it can be called via the EXECUTE PROCEDURE statement and it returns a single set of output parameters.

In Firebird 2.x only a selectable stored procedure can be "used" as a view / table (see Firebird Stored Procedures).

So:

SELECT FN_TEST(some_table_field) AS field_modified
FROM   tb_test

produces an invalid request BLR at offset... error.

You could change your procedure as suggested but, actually, the feature you need has been introduced in Firebird 3 in the form of stored function:

CREATE FUNCTION FN_TEST(Y INT) RETURNS INT
AS
BEGIN
  RETURN Y + 1;
END;

SELECT FN_TEST(4) AS zzz
FROM   tb_test

Further details in Functions with PSQL in Firebird 3.

Answer 2

Use UDF in order to manage calculation on fields. Stored procedure are admited only in the FROM Clause.