Code:
SQL> select * from employee;
LASTNAME DEPARTMENTID
-------------------- ------------
Rafferty 31
Jones 33
Steinberg 33
Robinson 34
Smith 34
John
6 rows selected.
SQL> select * from department;
DEPARTMENTID DEPARTMENTNAME
------------ --------------------
31 Sales
33 Engineering
34 Clerical
35 Marketing
SQL> select * from department d join employee e
2 using (departmentid);
DEPARTMENTID DEPARTMENTNAME LASTNAME
------------ -------------------- --------------------
31 Sales Rafferty
33 Engineering Jones
33 Engineering Steinberg
34 Clerical Robinson
34 Clerical Smith
SQL> delete from employee e
2 where exists ( select * from department d join employee e
3 using (departmentid));
6 rows deleted.In the above structure, table EMPLOYEE contains NULL value in the departmentid column which refers the lastname of JOHN.
when i delete EMPLOYEE table joining DEPARTMENT table using EXISTS, even the NULL value is also getting deleted .But i want JOHN record to be present while delting...I cant understand what mistake i did.
Can anyone help me getting the right query.