How can i fix this Mutating table from a procedure an trigger

Question

This trigger will pass on inserted values to a procedure which will insert those values in another table. I'm getting a mutating table error. How can i fix this?

CREATE OR REPLACE TRIGGER ADD_INVOICE
BEFORE INSERT OR UPDATE OF APP_NO,C_NO ON APPOINTMENT
FOR EACH ROW
DECLARE
BEGIN

POP_INVOICE(:NEW.APP_NO,:NEW.C_NO,:NEW.APP_DATE);

END;
/

CREATE OR REPLACE PROCEDURE POP_INVOICE(
I_APP_NO IN INVOICE.APP_NO%TYPE,
I_C_NO IN INVOICE.C_NO%TYPE,
I_INV_DATE IN INVOICE.INV_DATE%TYPE)
AS
CURSOR C_POP IS SELECT PRICE FROM TREATMENT T,APPOINTMENT A 
WHERE T.TRT_NO=A.TRT_NO
AND A.APP_NO=I_APP_NO;

V_BILL INVOICE.BILL%TYPE;
BEGIN

OPEN C_POP; 
FETCH C_POP INTO V_BILL;

UPDATE INVOICE
SET INV_NO=INV_IDSEQ.NEXTVAL,
APP_NO=I_APP_NO,
C_NO=I_C_NO,
BILL=V_BILL,
INV_DATE=I_INV_DATE;

END;
/

Answer 1

The problem is caused by referencing the table with the trigger on it within the trigger itself. Changing the procedure to accept the TRT_NO as a parameter removes the need to include APPOINTMENT in the query, and so will avoid the mutating table exception. Depending on how many records there are for each treatment, you could even incorporate the cursor into your UPDATE statement.

I think this should do it, although I haven't been able to check against a database.

CREATE OR REPLACE TRIGGER ADD_INVOICE

BEFORE INSERT OR UPDATE OF APP_NO,C_NO ON APPOINTMENT
FOR EACH ROW
DECLARE
BEGIN

POP_INVOICE(:NEW.APP_NO,:NEW.C_NO,:NEW.APP_DATE,:NEW.TRT_NO);

END;
/

The revised procedure:

CREATE OR REPLACE PROCEDURE POP_INVOICE(
I_APP_NO IN INVOICE.APP_NO%TYPE,
I_C_NO IN INVOICE.C_NO%TYPE,
I_INV_DATE IN INVOICE.INV_DATE%TYPE,
I_TRT_NO IN APPOINTMENT.TRT_NO%TYPE
)
AS

CURSOR C_POP IS SELECT PRICE 
FROM TREATMENT T
WHERE T.TRT_NO = I_TRT_NO;

V_BILL INVOICE.BILL%TYPE;

BEGIN

OPEN C_POP; 
FETCH C_POP INTO V_BILL;
CLOSE C_POP;

INSERT INVOICE
  (inv_no, app_no, c_no, bill, inv_date)
VALUES
  (INV_IDSEQ.NEXTVAL, I_APP_NO, I_C_NO, V_BILL, I_INV_DATE);


END;
/