[SQL] FOR EACH STATEMENT trigger ?

[F. BROUARD / SQLpro]

Hi there

I am trying to get an example of SET BASED trigger logic with FOR EACH
STATEMENT, but I cannot find any example involving the pseudo table NEW
(or OLD) in the trigger function SQL statement.

Let me give you a real life example.

Suppose we have the above table :

CREATE TABLE T_PRODUIT_DISPO_PDD
(PRD_ID         INT         NOT NULL,
 PDD_BEGIN      DATE        NOT NULL,
 PDD_END        DATE,
 PDD_QUANTITY   FLOAT       NOT NULL);

We want to never have more thant one PDD_END = NULL for the same PRD_ID.

The assertion we can do is :

ALTER TABLE T_PRODUIT_DISPO_PDD
   ADD CONSTRAINT CK_PDD_PRD_FIN_UNIQUENULL
      CHECK (NOT EXISTS(SELECT 0
                        FROM   T_PRODUIT_DISPO_PDD
                        WHERE  PDD_FIN IS NULL
                        GROUP  BY PRD_ID
                        HAVING COUNT(*) > 1))

Which is not supported by PG

So I wuld like to do this with a FOR EACH STATEMENT trigger and not by a
FOR EACH ROW.

Here is the code I try :

CREATE OR REPLACE FUNCTION F_UNIQUE_NULL_PRD_END() RETURNS trigger AS
$code$
DECLARE n_rows integer;
BEGIN
SELECT COUNT(*) INTO n_rows
WHERE EXISTS(SELECT 0
             FROM   T_PRODUIT_DISPO_PDD
             WHERE  PRD_ID IN(SELECT NEW.PRD_ID
                              FROM   NEW) AS T
               AND  PDD_END IS NULL
             GROUP  BY PRD_ID
             HAVING COUNT(*) > 1);
IF ( n_rows IS NOT NULL )
   THEN RAISE EXCEPTION 'Violation de la contrainte d''unicité sur le
couple de colonne PRD_ID + PDD_FIN';
   ROLLBACK TRANSACTION;
END IF;
RETURN NULL;
END
$code$ LANGUAGE 'plpgsql' VOLATILE

Which produce an error !

Of course I can do that with a FOR EACH STATEMENT like this one :

CREATE OR REPLACE FUNCTION F_UNIQUE_NULL_PRD_FIN() RETURNS trigger AS
$code$
DECLARE n_rows integer;
BEGIN
SELECT 1 INTO n_rows
WHERE EXISTS(SELECT 0
             FROM   T_PRODUIT_DISPO_PDD
             WHERE  PRD_ID = NEW.PRD_ID
               AND  PDD_FIN IS NULL
             GROUP  BY PRD_ID
             HAVING COUNT(*) > 1);
IF ( n_rows IS NOT NULL )
   THEN RAISE EXCEPTION 'Violation de la contrainte d''unicité sur le
couple de colonne PRD_ID + PDD_FIN';
   ROLLBACK TRANSACTION;
END IF;
RETURN NULL;
END
$code$ LANGUAGE 'plpgsql' VOLATILE

CREATE TRIGGER E_IU_PRD
   AFTER INSERT OR UPDATE
   ON T_PRODUIT_DISPO_PDD
   FOR EACH ROW EXECUTE PROCEDURE F_UNIQUE_NULL_PRD_FIN();


But it is absolutly not that I Want !!!!

Thanks


--
Frédéric BROUARD - expert SGBDR et SQL - MVP SQL Server - 06 11 86 40 66
Le site sur le langage SQL et les SGBDR  :  http://sqlpro.developpez.com
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