Learn the reason and how to resolve the ORA-04091 error message in Oracle.
Description
When you encounter an ORA-04091 error, the following error message will appear:
ORA-04091: table name is mutating, trigger/function may now not see it
Cause
A assertion performed a trigger or customized PL/SQL function. That trigger/function tried to adjust or question a desk that is presently being modified with the aid of the declaration that fired the trigger/function.
Resolution
The option(s) to resolve this Oracle error are:
Option #1
Re-write the trigger/function so that it does no longer strive to modify/query the desk in question.
For example, if you’ve got created a trigger in opposition to the desk known as orders and then the set off performed a SELECT against the orders desk as follows:
CREATE OR REPLACE TRIGGER orders_after_insert
AFTER INSERT
ON orders
FOR EACH ROW
DECLARE
v_quantity number;
BEGIN
SELECT quantity
INTO v_quantity
FROM orders
WHERE order_id = 1;
END;You would receive an error message as follows:
When you create a set off against a table, you can’t modify/query that desk until the trigger/function has completed.
Remember that you can constantly use the :NEW and :OLD values inside the trigger, depending on the type of trigger. Learn more about Triggers.