TRIGGER控制级联更新

CREATE TABLE AAAA
    (A  NUMBER  NOT NULL,
     CONSTRAINT PK_AAAA  PRIMARY  KEY (A) ) ;
CREATE TABLE  AAAAB
    (A  NUMBER  NOT NULL,
     B  VARCHAR2(20) NOT NULL,
     CONSTRAINT PK_AAAAB PRIMARY KEY (A),
     CONSTRAINT FK_AAAAB_AAAA  FOREIGN KEY (A)
     REFERENCE  AAAA(A) ) ;

--先更新主表再更新子表
CREATE OR REPLACE TRIGGER TR_AU_AAAA
AFTER UPDATE OF A ON AAAA
FOR EACH ROW
BEGIN
   UPDATE aaaab SET a=:new.a WHERE a=:old.a;
END;