SQL & PL/SQL

Hi,

I keep getting this error message for my trigger when performing an
insert..select statement (standard plain old insert works):

ORA-04091: table ... is mutating, trigger/function may not see it

The trigger is as follows:

CREATE OR REPLACE TRIGGER MYTABLE_BEF_INS_CHECK
BEFORE INSERT ON MYTABLE
DECLARE
v_o_id number(10);
BEGIN
IF :new.TYP = 'O' THEN
SELECT 1
INTO v_o_id
FROM MYTABLE WHERE TYP = 'O' AND ID=:new.ID;
END IF;
END;

The thing is the trigger works fine for a standard insert like:

insert into MYTABLE( id,typ)
values(426672,'O')

No problem the above works. But when I try an insert select..it
fails.

insert into MYTABLE( id,typ)
SELECT x_id, 'O' from AnyOtherTable;


the above will fail.

Anyone an idea why this is the case??

thx.