An user defined function must return a value, which can be used in any expression as long as the return value data type matches the expression.

To execute a user defined function and use its return value in an expression, you just need to enter the schema name and the function name as a value in the expression. The tutorial exercise below shows you how use a user defined function in an expression:

-- Calling a function without schema name

PRINT 'Hi there, '+Welcome();

GO

Msg 195, Level 15, State 10, Line 1

'Welcome' is not a recognized built-in function name.

-- Calling a function with schema name

PRINT 'Hi there, '+dbo.Welcome();

GO

Hi there, Welcome to rendc.org