ISNULL allows a display of the specified value as substitution for NULL
1>
2> CREATE TABLE works_on (emp_no INTEGER NOT NULL,
3> project_no CHAR(4) NOT NULL,
4> job CHAR (15) NULL,
5> enter_date DATETIME NULL)
6> GO
1> insert into works_on values (1, 'p1', 'analyst', '1997.10.1')
2> insert into works_on values (1, 'p3', 'manager', '1999.1.1')
3> insert into works_on values (2, 'p2', 'clerk', '1998.2.15')
4> insert into works_on values (2, 'p2', NULL, '1998.6.1')
5> insert into works_on values (3, 'p2', NULL, '1997.12.15')
6> insert into works_on values (4, 'p3', 'analyst', '1998.10.15')
7> insert into works_on values (5, 'p1', 'manager', '1998.4.15')
8> insert into works_on values (6, 'p1', NULL, '1998.8.1')
9> insert into works_on values (7, 'p2', 'clerk', '1999.2.1')
10> insert into works_on values (8, 'p3', 'clerk', '1997.11.15')
11> insert into works_on values (7, 'p1', 'clerk', '1998.1.4')
12> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1>
2> -- ISNULL allows a display of the specified value as substitution for NULL
3>
4> SELECT emp_no, ISNULL(job, 'Job unknown') task FROM works_on WHERE project_no = 'p1'
5> GO
emp_no task
----------- ---------------
1 analyst
5 manager
6 Job unknown
7 clerk
(4 rows affected)
1>
2> drop table works_on
3> GO
1>
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