SQL Avg

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

Syntax 
SELECT AVG(column_name) FROM table_name

The "custmast"  table

custcode	custname	city	qty	rate
1	Siva	Srivilliputtur	50	70
2	Bala	Sivakasi	30	56
3	Kanna	Madurai	100	200
4	Vijay	Chennai	30	30
5	Kodee	Sandnes	60	80
6	Vicky	Srivilliputtur	60	30

Example : 

SELECT AVG(Rate) AS AvgRate FROM Custmast

Output :

AvgRate

77.666666