SQL AVG() Function

The AVG() Function

The AVG() function returns the average value of a numeric column.

SQL AVG() Syntax

SELECT AVG(column_name) FROM table_name

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SQL AVG() Example

We have the following "Orders" table:

O_Id	OrderDate	OrderPrice	Customer
1	2008/11/12	1000	Hansen
2	2008/10/23	1600	Nilsen
3	2008/09/02	700	Hansen
4	2008/09/03	300	Hansen
5	2008/08/30	2000	Jensen
6	2008/10/04	100	Nilsen

Now we want to find the average value of the "OrderPrice" fields.


We use the following SQL statement:

SELECT AVG(OrderPrice) AS OrderAverage FROM Orders

The result-set will look like this:

OrderAverage

950

Now we want to find the customers that have an OrderPrice value higher than the average OrderPrice value.


We use the following SQL statement:

SELECT Customer FROM Orders WHERE OrderPrice>(SELECT AVG(OrderPrice) FROM Orders)

The result-set will look like this:

Customer

Hansen

Nilsen

Jensen

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SQL COUNT(*) Example

If we omit the WHERE clause, like this:

SELECT COUNT(*) AS NumberOfOrders FROM Orders

The result-set will look like this:

NumberOfOrders

6

which is the total number of rows in the table.

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SQL COUNT(DISTINCT column_name) Example

Now we want to count the number of unique customers in the "Orders" table.


We use the following SQL statement:

SELECT COUNT(DISTINCT Customer) AS NumberOfCustomers FROM Orders

The result-set will look like this:

NumberOfCustomers

3

which is the number of unique customers (Hansen, Nilsen, and Jensen) in the "Orders" table.

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Posted in: SQL Tutorial