sql - Trigger compilation error -

i need in creating trigger.

create or replace trigger trigger_one  before insert on funtom_timesheet each row declare v_id    number; v_hours number; begin select max(timesheet_id)+1 v_id funtom_timesheet :new.timesheet_id :=v_id; select grade_hours v_hours funtom_grade join funtom_employee on emp_grade = grade_id empid = :new.timesheet_emp; if v_hours >:new.timesheet_hours else :new.timesheet_overtime := :new.timesheet_hours-v_hours :new.timesheet_hours:= v_hours; end if; end; / 

please tell me part of code wrong work on it, thanks

you have many syntax errors - missing ; , then. there can't if else part , without expression on it.

create or replace trigger trigger_one   before insert on funtom_timesheet   each row declare   v_id    number;   v_hours number; begin   select max(timesheet_id) + 1 v_id funtom_timesheet;   :new.timesheet_id := v_id;   select grade_hours     v_hours     funtom_grade     join funtom_employee       on emp_grade = grade_id    empid = :new.timesheet_emp;   if v_hours > :new.timesheet_hours     null;   else     :new.timesheet_overtime := :new.timesheet_hours - v_hours;     :new.timesheet_hours    := v_hours;   end if; end; / 

also better use sequences instead of:

select max(timesheet_id) + 1 v_id funtom_timesheet; :new.timesheet_id := v_id; 

when selecting form same table inserting, can mutating trigger error (http://www.dba-oracle.com/t_avoiding_mutating_table_error.htm)