Trigger in oracle SQL - Validation? -

hello guys i'm trying create trigger validate data, i've got table called 'events' , need create trigger give me error when try add event in july.

create or replace trigger concert_trigger after insert on concert when (event_date = 'july') begin alter table concert add constraint chk_concert check (event.date ='july') end;

here trigger have started think way go i'm not sure if right.

thanks, leprejohn

since classwork requires use of trigger you'd want like

create or replace trigger concert_bi   before insert on concert   each row begin   if to_char(event_date, 'mon') = 'jul'     raise_application_error(-20666, 'no concerts can scheduled in july');   end if; end concert_bi; 

here i'm assuming event_date actual date instead of character string; if bad guess change comparison appropriately.

share , enjoy.