Mega Code Archive

NVL() is used to convert null in correlated query

SQL> SQL> -- create demo table SQL> create table Employee( 2 empno Number(3) NOT NULL, -- Employee ID 3 ename VARCHAR2(10 BYTE), -- Employee Name 4 hireDate DATE, -- Date Employee Hired 5 orig_salary Number(8,2), -- Orignal Salary 6 curr_salary Number(8,2), -- Current Salary 7 region VARCHAR2(1 BYTE) -- Region where employeed 8 ) 9 / Table created. SQL> SQL> create table job( 2 empno Number(3), -- Employee ID 3 jobtitle VARCHAR2(10 BYTE) -- Employee job title 4 ) 5 / Table created. SQL> -- prepare data for employee table SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(122,'Alison',to_date('19960321','YYYYMMDD'), 45000, 48000, 'E') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(123, 'James',to_date('19781212','YYYYMMDD'), 23000, 32000, 'W') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(104,'Celia',to_date('19821024','YYYYMMDD'), 53000, 58000, 'E') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(105,'Robert',to_date('19840115','YYYYMMDD'), 31000, 36000, 'W') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(116,'Linda', to_date('19870730','YYYYMMDD'), 43000, 53000, 'E') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(117,'David', to_date('19901231','YYYYMMDD'), 78000, 85000, 'W') 3 / 1 row created. SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region) 2 values(108,'Jode', to_date('19960917','YYYYMMDD'), 21000, 29000, 'E') 3 / 1 row created. SQL> SQL> -- prepare data for job table SQL> SQL> insert into job(empno, jobtitle) 2 values(101, 'Painter'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(122, 'Tester'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(123, 'Dediator'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(104, 'Chemist'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(105, 'Accountant'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(116, 'Manager'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(117, 'Programmer'); 1 row created. SQL> SQL> insert into job(empno, jobtitle) 2 values(NULL, 'Developer'); 1 row created. SQL> SQL> SQL> -- display data in the table SQL> select * from Employee 2 / EMPNO ENAME HIREDATE ORIG_SALARY CURR_SALARY R ---------- ---------- ----------- ----------- ----------- - 122 Alison 1996-MAR-21 45000 48000 E 123 James 1978-DEC-12 23000 32000 W 104 Celia 1982-OCT-24 53000 58000 E 105 Robert 1984-JAN-15 31000 36000 W 116 Linda 1987-JUL-30 43000 53000 E 117 David 1990-DEC-31 78000 85000 W 108 Jode 1996-SEP-17 21000 29000 E 7 rows selected. SQL> SQL> select * from job; EMPNO JOBTITLE ---------- ---------- 101 Painter 122 Tester 123 Dediator 104 Chemist 105 Accountant 116 Manager 117 Programmer Developer 8 rows selected. SQL> SQL> SQL> SQL> SQL> --NVL() is used to convert null in correlated query SQL> SQL> SELECT empno, ename 2 FROM employee 3 WHERE empno NOT IN 4 (SELECT NVL(empno, 0) 5 FROM job); EMPNO ENAME ---------- ---------- 108 Jode SQL> SQL> SQL> drop table job; Table dropped. SQL> SQL> -- clean the table SQL> drop table Employee 2 / Table dropped. SQL> SQL> SQL>