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mysqlsqltriggersmysql5

what does trigger's IF syntax mean in following program?

DELIMITER $$  
create trigger mytable_check before insert on test.mytable for each row  
begin  
 if new.id_category in ('list','of','special','categories')  
    and exists  
      (select * from mytable  
       where id_category=new.id_category  
         and keywords=new.keywords) then  
    call fail(concat('id_category,keywords must be unique when id_category is: ',new.id_category));  
 end if;  
end $$  
DELIMITER ;

I am having slight problem in understanding this trigger statement. Can u please explain me this statement?What does

if new.id_category in ('list','of','special','categories')

statement mean??

Solution 
  • new.id_category = 'list'
or
new.id_category = 'of'
or
new.id_category = 'special'
or
new.id_category = 'categories'