RAISERRORに相当するMySQL

Question

RAISERRORと同等のSQL Serverは何ですか？

CREATE procedure GetallFiles() 
as 
begin 
if not exists(select files.Files,Users.FirstName,Users.LastName,Users.EmailAddress from files,Users 
where files.UserID = Users.UserID) 
raiserror('cannot find files records',16,1) 
end 
begin 

select files.Files,Users.firstname,Users.lastname,Users.EmailAddress from files,Users 
where files.UserID = Users.UserID 
end 
return 

Answer 1

SET @s = 'Unknown condition type !'; 
    SIGNAL SQLSTATE '45001' SET MESSAGE_TEXT = @s;