主键和外键的问题

trigger ?定义外键的时候有一个验证约束的延迟的ALTER TABLE AAA ADD (CONSTRAINT AAA_PK PRIMARY KEY(a) DEFERRABLE) ;

ALTER TABLE BBB
    ADD (CONSTRAINT BBB_FK FOREIGN KEY(a)
    REFERENCES AAA(a)
    ON DELETE CASCADE DEFERRABLE)
    CREATE OR REPLACE TRIGGER ID_TRG AFTER UPDATE ON AAA FOR EACH ROW
BEGIN
UPDATE BBB SET a=:NEW.a WHERE a=:OLD.a;
END;