问题
I have a trigger like this: (Basically on update of a column in table1, I update a column in table 2)
CREATE OR REPLACE TRIGGER AAA AFTER UPDATE
ON TABLE_1 REFERENCING NEW AS NEWROW OLD AS OLDROW
FOR EACH ROW
WHEN (
NEWROW.DELETED ='Y' AND NEWROW.ID IN (41,43)
AND OLDROW.DELETED = 'N'
)
DECLARE
id_1 number;
id_2 number;
id_3 number;
BEGIN
select id_1, id_2,id_3 into id_1,id_2,id_3 from table_1 where id_1 = :NEWROW.id1 and id2 = some_other_row.id2;
if id_1 is null
then
update table2 set deleted = 'Y' , where table2.id_1 = id_1 and table2.id_2=id_2 and table2.id_3 = id_3;
end if;
EXCEPTION
WHEN OTHERS
THEN
-- Consider logging the error and then re-raise
RAISE;
END AAA;
/
When I update table1 I get:
ORA-04091: table table1 is mutating, trigger/function may not see it
I thought this error happens only when you are updating the table on which the trigger is trying to update something. But here I am updating table1 and trigger is supposed to update table2. SO why is the error?
回答1:
It's the SELECT statement that is causing the problem here. Inside the trigger, you cannot SELECT from the same table. In your example, you don't need/can't use the SELECT statement. You can get the values by simply using :newrow.id_1, :newrow.id_2 and :newrow.id_3.
来源：https://stackoverflow.com/questions/16800709/unusual-table-table1-is-mutating-trigger-function-may-not-see-it-error-in-oracl