sql - Create a trigger -

create trigger called newentry, not allow result inserted student exam table if less zero. in query display suitable message if result less 0 , supply code test trigger.

this have done, keep getting

warning : trrigger created compilation errors.

this code, please help!

create or replace trigger newentry  after insert or update on assignment2.student_exam  each row declare results number; begin if(:new.results < '0') raise_application_error (-20700,'student's result cannot less-than zero..enter valid results':); endif; end;  / 

end if, not endif. jeremy c mentions above need create trigger before insert or update