Trigger compilé sans erreur mais ne fonctionne pas

CREATE TABLE Cpt (
 idcompte VARCHAR(15) NOT NULL PRIMARY KEY,
 tipe  VARCHAR(20) NOT NULL,
 nom_banque VARCHAR(20) NOT NULL,
 solde  FLOAT NOT NULL,
 idclient INTEGER NOT NULL
);

CREATE TABLE Op (
 idoperation INTEGER NOT NULL PRIMARY KEY,
 type_operation VARCHAR(6) NOT NULL,
 date_operation Date NOT NULL,
 libelle  VARCHAR(50) NOT NULL,
 somme  FLOAT NOT NULL,
 idcompte VARCHAR(15) NOT NULL
);

create or replace trigger Maj_compte
  before delete or update or insert on op  
  for each row
 
declare
  old_somme Op.somme%TYPE DEFAULT 0;
  somme_tmp Op.somme%TYPE DEFAULT 0;
  PRAGMA autonomous_transaction;
begin
 
   IF DELETING THEN
   SELECT somme INTO somme_tmp FROM Op WHERE idoperation = :OLD.idoperation;
   UPDATE Cpt SET solde = (solde - somme_tmp) WHERE idcompte = ':OLD.idcompte';
  END IF;
 
  IF INSERTING THEN
   SELECT somme INTO somme_tmp FROM Op WHERE idoperation = :NEW.idoperation;
   UPDATE Cpt SET solde = (solde + somme_tmp) WHERE idcompte = ':NEW.idcompte';
  END IF;
 
  IF UPDATING THEN
   SELECT somme INTO old_somme FROM Op WHERE idoperation = :OLD.idoperation;
   IF old_somme > :OLD.somme THEN
    UPDATE Cpt SET solde = (solde - (old_somme - :OLD.somme)) WHERE idcompte = ':NEW.idcompte';
   ELSE
    UPDATE cpt SET solde = (solde + (:OLD.somme - old_somme)) WHERE idcompte = ':NEW.idcompte';
   END IF;
  END IF;
    EXCEPTION WHEN NO_DATA_FOUND THEN NULL;    
  
end Maj_compte;