Use aggregate function MAX in subquery : Subquery Aggregate Functions « Subquery « SQL Server / T-SQL





Use aggregate function MAX in subquery


1> CREATE TABLE works_on        (emp_no       INTEGER NOT NULL,
2>                         project_no    CHAR(4) NOT NULL,
3>                         job CHAR (15) NULL,
4>                         enter_date    DATETIME NULL)
5>
6> insert into works_on values (1, 'p1', 'analyst', '1997.10.1')
7> insert into works_on values (1, 'p3', 'manager', '1999.1.1')
8> insert into works_on values (2, 'p2', 'clerk',   '1998.2.15')
9> insert into works_on values (2, 'p2',  NULL,     '1998.6.1')
10> insert into works_on values (3, 'p2',  NULL,     '1997.12.15')
11> insert into works_on values (4, 'p3', 'analyst', '1998.10.15')
12> insert into works_on values (5, 'p1', 'manager', '1998.4.15')
13> insert into works_on values (6, 'p1',  NULL,     '1998.8.1')
14> insert into works_on values (7, 'p2', 'clerk',   '1999.2.1')
15> insert into works_on values (8, 'p3', 'clerk',   '1997.11.15')
16> insert into works_on values (7, 'p1', 'clerk',   '1998.1.4')
17> 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> select * from works_on
3> GO
emp_no      project_no job             enter_date
----------- ---------- --------------- -----------------------
          1 p1         analyst         1997-10-01 00:00:00.000
          1 p3         manager         1999-01-01 00:00:00.000
          2 p2         clerk           1998-02-15 00:00:00.000
          2 p2         NULL            1998-06-01 00:00:00.000
          3 p2         NULL            1997-12-15 00:00:00.000
          4 p3         analyst         1998-10-15 00:00:00.000
          5 p1         manager         1998-04-15 00:00:00.000
          6 p1         NULL            1998-08-01 00:00:00.000
          7 p2         clerk           1999-02-01 00:00:00.000
          8 p3         clerk           1997-11-15 00:00:00.000
          7 p1         clerk           1998-01-04 00:00:00.000

(11 rows affected)
1>
2> -- Use aggregate function MAX.
3>
4> SELECT emp_no FROM works_on WHERE enter_date =
5>        (SELECT MAX(enter_date)
6>          FROM works_on WHERE job = 'manager')
7> GO
emp_no
-----------
          1

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










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