SQL Server/T-SQL/Subquery/Subquery Aggregate Functions
Use aggregate function in subquery
1> CREATE TABLE employee (emp_no INTEGER NOT NULL,
2> emp_fname CHAR(20) NOT NULL,
3> emp_lname CHAR(20) NOT NULL,
4> dept_no CHAR(4) NULL)
5>
6> insert into employee values(1, "Matthew", "Smith", "d3")
7> insert into employee values(2, "Ann", "Jones", "d3")
8> insert into employee values(3, "John", "Barrimore","d1")
9> insert into employee values(4, "James", "James", "d2")
10> insert into employee values(5, "Elsa", "Bertoni", "d2")
11> insert into employee values(6, "Elke", "Hansel", "d2")
12> insert into employee values(7, "Sybill", "Moser", "d1")
13>
14> select * from employee
15> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
emp_no emp_fname emp_lname dept_no
----------- -------------------- -------------------- -------
1 Matthew Smith d3
2 Ann Jones d3
3 John Barrimore d1
4 James James d2
5 Elsa Bertoni d2
6 Elke Hansel d2
7 Sybill Moser d1
(7 rows affected)
1> -- Get the number and the last name of the employee with the smallest employee number.
2>
3> SELECT emp_no, emp_lname FROM employee
4> WHERE emp_no = (SELECT MIN(emp_no) FROM employee)
5> GO
emp_no emp_lname
----------- --------------------
1 Smith
(1 rows affected)
1>
2> drop table employee
3> GO
1>
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>