Limitations or Restriction in SQL Functions.

•   Function cannot be used to perform action that can modify data ex. Insert, Update & Delete.

• User-defined functions cannot return multiple result sets. Functions return single value or table.

• Function does not support Error handling. TRY…CATCH, @ERROR or RAISERROR are restricted.

• Functions cannot call a stored procedure, but can call an extended stored procedure.

• We can’t use dynamic SQL or temp tables in functions. Table variables are allowed.

•  SET statements are not allowed in a user-defined function. Ex set ROWCOUNT etc.

•  User Defined Function can't returns XML Data Type.

•  User-defined functions can be nested; that is, one user-defined function can call another. 

• Function can be nested up to 32 levels. 

•   Function accepts only input parameters (unlike stored procedure).