how to use function in sql server with simple example

hi,

Please refer below link to know what is function and how to create function
http://msdn.microsoft.com/en-in/library/ms186755.aspx

There are four main type of function in SQL server

1) table Valued function : that return whole table
 select * from myTableFunction()
2) Scalar Value function : It return signle column and row value
 select myscalaeFunction()
3) Aggregate function : it is inbuit Aggregate like sum, count etc..
4) system function

also refer
http://www.dotnet-tricks.com/Tutorial/sqlserver/KY3T010412-Different-Types-of-SQL-Server-Functions.html

hope this will help you.