What is instead of triggers in SQL?
An INSTEAD OF trigger is an SQL trigger that is processed “instead of” an SQL UPDATE, DELETE or INSERT statement. Unlike SQL BEFORE and AFTER triggers, an INSTEAD OF trigger can be defined only on a view, not a table. INSTEAD OF triggers can simplify the maintenance of access control to tables.
Does MySQL support instead of triggers?
2 Answers. MySQL does not have instead of triggers, but it does have REPLACE and INSERT… ON DUPLICATE KEY UPDATE (see documentation).
What is instead of triggers & its usage?
INSTEAD OF triggers provide a transparent way of modifying views that cannot be modified directly through DML statements ( INSERT , UPDATE , and DELETE ). These triggers are called INSTEAD OF triggers because, unlike other types of triggers, Oracle fires the trigger instead of executing the triggering statement.
What is instead of update trigger?
INSTEAD OF UPDATE triggers correctly update a View that is based on multiple tables. Description. This INSTEAD OF UPDATE trigger is executed instead of an update event, on a table or a View.
What is instead of DML trigger?
An INSTEAD OF trigger is a trigger that allows you to update data in tables via their view which cannot be modified directly through DML statements. If the view has an INSTEAD OF trigger, it will automatically skip the DML statement and execute other DML statements instead.
What are the syntax of using MySQL triggers?
Use the BEGIN and END delimiters to indicate the trigger body: CREATE TRIGGER > ON
How many instead of trigger is it possible to create for this table?
You can specify only one first and one last AFTER trigger for each INSERT, UPDATE, and DELETE operation on a table.
What happens during Instead of insert trigger?
INSTEAD OF triggers cause their source DML operation to skip and they just execute the code provided inside them. Actual insert, delete or update operation do not occur at all. However they have their associated inserted and deleted tables simulating the DML operation.
What is the difference between instead of and after for trigger?
AFTER trigger fires after a DML operation. INSTEAD OF trigger fires instead of a DML operation.
Why we use triggers in MySQL?
We need/use triggers in MySQL due to the following features: Triggers help us to enforce business rules. Triggers help us to validate data even before they are inserted or updated. Triggers help us to keep a log of records like maintaining audit trails in tables.