SQL & PL/SQL

Hi,

i try to implement a check constraint.
I have written it in this way:

ALTER TABLE SPR_KLERS_IGA_APPO
  ADD CONSTRAINT SPR_KLERS_IGA_APPO_CEG CHECK (
    (SELECT CHECK_IGA_OBJ(SPR_KLERS_IGA_APPO.CODICE_ENTE_GARANTE)
       FROM DUAL) > 0
)

The function named CHECK_IGA_OBJ is

FUNCTION FIN.CHECK_IGA_OBJ(COD_GAR IN VARCHAR2) RETURN NUMBER
IS
    IGA_RESULT NUMBER;
    IEM_RESULT NUMBER;
    BEGIN
         SELECT COUNT(*)
           INTO IGA_RESULT
           FROM SPR_KLERS_IGA_GARANTE
          WHERE ID = COD_GAR;       
         
         SELECT COUNT(*)
           INTO IEM_RESULT
           FROM SPR_KLERS_IEM
          WHERE EMICOD = COD_GAR;
          
          IF IGA_RESULT > IEM_RESULT THEN
             RETURN IGA_RESULT;
          ELSE
             RETURN IEM_RESULT;
          END IF;
          
    END CHECK_IGA_OBJ;

When I try to execute the constraint code I receive the following error:

ORA-02251: subquery not allowed here

.

I would assign this type of constraint to the column 'SPR_KLERS_IGA_APPO.CODICE_ENTE_GARANTE'
because the values, for this column, are contained in two columns of two tables.
My goal is the implementation of an integrity constraint.

Is this the correct way to face the problem?

byebye

Edited by: Abdujaparov on Oct 20, 2008 2:13 PM