>Sergey,
>
>If I want to pass part of the string and return a whole string, should I use SP or UDF?
I'm not sure what you mean. You can use either. Create UDF if you want to use it in a query.
>
>Writing SPs is so hard for beginner!

It's easier that writing VFP functions/procedures because T-SQL much less built-in functions and commands. :)