Oracle trigger error ORA-04091

Question

I get an error (ORA-04091: table DBPROJEKT_AKTIENDEPOT.AKTIE is mutating, trigger/function may not see it) when executing my trigger:

CREATE OR REPLACE TRIGG         


        

Answer 1

You are modifying the table with the trigger. Use a before update trigger:

CREATE OR REPLACE TRIGGER Aktien_Bilanz_Berechnung
BEFORE INSERT OR UPDATE OF TAGESKURS OR INSERT OR UPDATE OF  WERT_BEIM_EINKAUF
ON AKTIE
FOR EACH ROW
DECLARE
    v_bfr number;
BEGIN
    v_bfr := :new.TAGESKURS - :new.WERT_BEIM_EINKAUF;
    :new.BILANZ := v_bfr;
    IF v_bfr < -50 THEN
      Raise_Application_Error(-20456,'ACHTUNG: The value (Nr: '|| :new.AKTIEN_NR || ') is very low!');
    END IF;
END;