Learn the cause and how to resolve the ORA-04091 error message in Oracle.
When you encounter an ORA-04091 error, the following error message will appear:
The option(s) to resolve this Oracle error are:
Re-write the trigger/function so that it does not try to modify/query the table in question.
For example, if you've created a trigger against the table called orders and then the trigger performed a SELECT against the orders table 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 trigger against a table, you can't modify/query that table until the trigger/function has completed.
Remember that you can always use the :NEW and :OLD values within the trigger, depending on the type of trigger. Learn more about Triggers.