DELETE from sys_user_function

    where User_Id = 19 and Function_Id in (

      select s.Function_Id from sys_user_function s where s.User_Id=19

    )

delete from sys_user_function where User_Id = 19 AND

Function_Id in

(

select a.Function_Id from

(

select max(Function_Id) Function_Id from sys_user_function a where a.User_Id=20 and EXISTS

(

select 1 from sys_user_function b where a.User_Id=b.User_Id group by User_Id HAVING count(1)>=1

)

group by Function_Id

) a

)