SELECT AVG(<field>) FROM <table>

AVG returns an average value of a group of values.

Table: Customers

OrderID	Customer	Employee	Order Date	ShippedVia	Freight	ShipCountry
10248	Wilman Kala	Buchanan, Steven	04-07-1996	Federal Shipping	32.38	France
10249	Hanari Carnes	Peacock, Margaret	08-07-1996	United Package	65.83	Brazil
10250	Hanari Carnes	Leverling, Janet	08-07-1996	United Package	58.17	Brazil
10251	Chop-suey Chinese	Buchanan, Steven	11-07-1996	United Package	22.98	Switzerland
10252	Richter Supermarkt	Dodsworth, Anne	12-07-1996	Federal Express	148.33	Switzerland

The following SQL statement returns 65.538.

SELECT AVG(Freight) FROM Orders

(32.38 + 65.83 + 58.17 + 22.98 + 148.33) / 5 = 65.538