Appendix B
Page 492

Example B-2

The Mutation Problem is Back-Caused by a Cascaded Delete from a Parent

CREATE TABLE dept(deptno NUMBER(4) NOT NULL
                      ,dname VARCHAR2(20) NOT NULL
                      ,loc   VARCHAR2(20) NOT NULL
                       ,CONSTRAINT dept_pk PRIMARY KEY (deptno));

INSERT INTO dept VALUES(10, 'DIRECT SALES ', 'BOSTON ');
INSERT INTO dept VALUES(11, 'CLEANING ', 'NEWARK ');
ALTER TABLE emp ADD CONSTRAINT emp_fk1 FOREIGN KEY (deptno)
REFERENCES dept(deptno) ON DELETE CASCADE;

DELETE FROM dept WHERE deptno = 10;

>ERROR at line 1:
>ORA-04091: table SCOTT.EMP is mutating, trigger/function may not see \
it
>ORA-06512: at "SCOTT.PK_EMP_MGR", line 19
>ORA-06512: at line 2
>ORA-04088: error during execution of trigger 'SCOTT.EMP_AD'