Using DISTINCT in Aggregate Functions : AVG « Aggregate Functions « SQL Server / T-SQL Tutorial

1. SQL Server / T-SQL Tutorial
2. Aggregate Functions
3. AVG

3>
4> CREATE TABLE employee(
5>    id          INTEGER NOT NULL PRIMARY KEY,
6>    first_name  VARCHAR(10),
7>    last_name   VARCHAR(10),
8>    salary      DECIMAL(10,2),
9>    start_Date  DATETIME,
10>    region      VARCHAR(10),
11>    city        VARCHAR(20)
12> );
13> GO
1> INSERT INTO employee VALUES (1, 'Jason' ,  'Martin', 5890,'2005-03-22','North','Vancouver');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (2, 'Alison',  'Mathews',4789,'2003-07-21','South','Utown');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (3, 'James' ,  'Smith',  6678,'2001-12-01','North','Paris');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (4, 'Celia' ,  'Rice',   5567,'2006-03-03','South','London');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (5, 'Robert',  'Black',  4467,'2004-07-02','East','Newton');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (6, 'Linda' ,  'Green' , 6456,'2002-05-19','East','Calgary');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (7, 'David' ,  'Larry',  5345,'2008-03-18','West','New York');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (8, 'James' ,  'Cat',    4234,'2007-07-17','West','Regina');
2> GO

(1 rows affected)
1> INSERT INTO employee VALUES (9, 'Joan'  ,  'Act',    6123,'2001-04-16','North','Toronto');
2> GO

(1 rows affected)
1>
2> select * from employee;
3> GO
id          first_name last_name  salary       start_Date              region     city
----------- ---------- ---------- ------------ ----------------------- ---------- --------------------
          1 Jason      Martin          5890.00 2005-03-22 00:00:00.000 North      Vancouver
          2 Alison     Mathews         4789.00 2003-07-21 00:00:00.000 South      Utown
          3 James      Smith           6678.00 2001-12-01 00:00:00.000 North      Paris
          4 Celia      Rice            5567.00 2006-03-03 00:00:00.000 South      London
          5 Robert     Black           4467.00 2004-07-02 00:00:00.000 East       Newton
          6 Linda      Green           6456.00 2002-05-19 00:00:00.000 East       Calgary
          7 David      Larry           5345.00 2008-03-18 00:00:00.000 West       New York
          8 James      Cat             4234.00 2007-07-17 00:00:00.000 West       Regina
          9 Joan       Act             6123.00 2001-04-16 00:00:00.000 North      Toronto

(9 rows affected)
1>
2>
3> SELECT AVG(DISTINCT salary)
4> FROM employee;
5> GO

----------------------------------------
                             5505.444444

(1 rows affected)
1>
2>
3>
4>
5> drop table employee;
6> GO