EXISTS evaluates to true if its result contains at least one row : Subqueries Exists « Subquery « SQL Server / T-SQL

1. SQL Server / T-SQL
2. Subquery
3. Subqueries Exists

EXISTS evaluates to true if its result contains at least one row

3>
4> CREATE TABLE works_on        (emp_no       INTEGER NOT NULL,
5>                         project_no    CHAR(4) NOT NULL,
6>                         job CHAR (15) NULL,
7>                         enter_date    DATETIME NULL)
8>
9> insert into works_on values (1, 'p1', 'analyst', '1997.10.1')
10> insert into works_on values (1, 'p3', 'manager', '1999.1.1')
11> insert into works_on values (2, 'p2', 'clerk',   '1998.2.15')
12> insert into works_on values (2, 'p2',  NULL,     '1998.6.1')
13> insert into works_on values (3, 'p2',  NULL,     '1997.12.15')
14> insert into works_on values (4, 'p3', 'analyst', '1998.10.15')
15> insert into works_on values (5, 'p1', 'manager', '1998.4.15')
16> insert into works_on values (6, 'p1',  NULL,     '1998.8.1')
17> insert into works_on values (7, 'p2', 'clerk',   '1999.2.1')
18> insert into works_on values (8, 'p3', 'clerk',   '1997.11.15')
19> insert into works_on values (7, 'p1', 'clerk',   '1998.1.4')
20> 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> -- EXISTS evaluates to true if its result contains at least one row
3>
4> SELECT job FROM works_on WHERE exists (SELECT emp_no FROM employee)
5> GO
job
---------------
analyst
manager
clerk
NULL
NULL
analyst
manager
NULL
clerk
clerk
clerk

(11 rows affected)
1>
2> drop table works_on
3> GO
1>
           
       

Related examples in the same category