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 ^ ;
CREATE PROCEDURE FN_TEST( Y INTEGER )
RETURNS( X INTEGER)
AS
BEGIN
X = Y + 1;
END^
SET TERM ; ^

I want to list some field of table modified by some procedure, like this:

SELECT some_table_field_1, 
       fn_test( 4 ) AS zzz, 
       some_table_field_2,
       fn_test( some_table_field_2 ) AS field_2_modified
FROM   tb_test

Need results (table):

some_table_field_1     zzz         some_table_field_2      field_2_modified
---------------------------------------------------------------------------
aaa                    5           14                      15
bbb                    5           23                      24
www                    5           75                      76

This thing works fine in PostgreSQL, but I don't know how to do this in Firebird.

Answer 1

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

Answer 2

You can use EXECUTE BLOCK Please have a look EXECUTE BLOCK

Answer 3

Try this

SET TERM ^ ;
CREATE PROCEDURE FN_TEST( Y INTEGER )
RETURNS( X INTEGER)
AS
BEGIN
X = Y + 1;
SUSPEND;
END^
SET TERM ; ^

Answer 4

SELECT some_table_field_1, 
   (select X from fn_test( 4 )) AS zzz, 
   some_table_field_2,
   (select X from fn_test( some_table_field_2 )) AS field_2_modified
FROM   tb_test

Answer 5

Try

SELECT some_table_field_1, 
   fn_test.x AS zzz, 
   some_table_field_2,
FROM   tb_test
LEFT JOIN fn_test(some_table_field_1) ON (1 = 1)

Answer 6

As JustMe said, you can't call stored procedures in a select. You can call stored procedure only in the FROM section. Another solution for your problem is to create a selectable procedure like this:

create or alter procedure myproc (
 n integer)
returns (
 field_1 integer,
 zzz integer,
 field_2 integer,
 modified_field_2 integer)
as
declare variable i integer;
begin
  for
    select some_table_field_1, :n+1 as zzz, some_table_field_2, (some_table_field_2+1) as field_2_modified
    from tb_test
    into :field_1, :zzz, :field_2, :modified_field_2
  do begin
    suspend;
  end
end

After run that code, you can simply query select * from myproc(4) and get what you want.