Parameter in Trigger

Question

Hi All,
I want to write a trigger on table to delete data from that table for a particular id before insert any new data for that particular id.
so how can i pass that id in trigger and how i will manage to execute this trigger once only i.e othewise it will delete 1st inserted row before inserting 2nd row and finally i will get only last inserted into table.
I hope you all got my problem.
Help me.
Thanks.
Anil Raghuvanshi

Answer 1

Hi,
I m working on mysql.
My table structure is as follow
id p_id feature
1 2 a
2 2 b
3 3 z
4 3 f
now i want to write a trigger on this table before inserting any new data for any p_id if data is thr in this(same) table then delete else insert the new data.
if i want to insert 3 records for p_id= 4 then they should insert and if i want to insert 4 new record for p_id=3 then first it should delete all the records for p_id =3 then it sgould insert new 4 records.
and i wrote following trigger for this
create or replace trigger test before insert on topthings
     If new.phone_id = old.phone_id then
     delete from topthings where phone_id:=new.phone_id;
     end If;
end;
It gets created but when i insert any record in table then it is giviing me error like
Can't update table 'topthings' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
Here i did't use for each row because as i insert 1st it will delete all previously exists rows then 1st inserted row before inserting 2nd row it will delete 1st inserted and finally i will get only last inserted row into table.
i hope you got my prob.
Thanks for the help.