What is instead of trigger?
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.
Can we create instead of trigger on table?
In Oracle, you can create an INSTEAD OF trigger for a view only. You cannot create an INSTEAD OF trigger for a table.
What are other uses of triggers?
Triggers allow you to perform the following tasks: Enforce business rules. Validate input data. Generate a unique value for a newly inserted row on a different file (surrogate function)
What are different types of triggers in Oracle?
Answer: There are two types of triggers in PL/SQL. They are Row-level trigger and Statement-level trigger.
What is after and instead of trigger?
1. Action Query: In the “After Trigger” the table data is affected after the execution of the action query whereas the table data isn’t affected after the execution of an action query in an “Instead of Trigger”.
Do triggers slow down database?
The triggers of this type will not slow down operations, however, will ensure data coupling and integrity. Every time I experienced “lags” when adding data to a table with a trigger, it was an example of such a “heavy” query.
Can we create triggers on views?
Triggers may be created on views, as well as ordinary tables, by specifying INSTEAD OF in the CREATE TRIGGER statement. If one or more ON INSERT, ON DELETE or ON UPDATE triggers are defined on a view, then it is not an error to execute an INSERT, DELETE or UPDATE statement on the view, respectively.
What are other uses of triggers in SQL?
Because a trigger resides in the database and anyone who has the required privilege can use it, a trigger lets you write a set of SQL statements that multiple applications can use. It lets you avoid redundant code when multiple programs need to perform the same database operation.
Should I use database triggers?
Triggers are a requirement for any complex data integrity rules. These cannot be enforced anywhere except the database or you will have data integrity problems. They are also the best place for auditing unless you don’t want to capture all changes to the database (which is the problem of auditing from the application).
Can we use commit in trigger?
You can’t commit inside a trigger anyway. Show activity on this post. Trigger should not commit and cannot commit. Committing in a trigger usually raises an exception unless it happens into autonomous transaction.
How many different types of triggers can exist in a table in Oracle?
12
You can create as many as you want. But With Oracle 9.0 or below maximum number of triggers is 12.
What are instead of triggers in Oracle?
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 the difference between for trigger and instead of trigger?
Why triggers are not recommended?
Triggers can cause performance issues if not written carefully and not enough developers are knowledgeable enough to write them well. This is part of where they get their bad rap.
Are triggers useful or damaging?
Triggers are useful if you need to be sure that certain events always happen when data is inserted, updated or deleted. This is the case when you have to deal with complex default values of columns, or modify the data of other tables. You can use external code as a trigger by using CLR triggers.
Can we use DDL in trigger?
DDL triggers fire only after the DDL statements that trigger them are run. DDL triggers cannot be used as INSTEAD OF triggers. DDL triggers do not fire in response to events that affect local or global temporary tables and stored procedures. DDL triggers do not create the special inserted and deleted tables.
Can you commit inside a trigger?
What is the difference between trigger and stored procedure?
Stored procedures can be invoked explicitly by the user. It’s like a java program , it can take some input as a parameter then can do some processing and can return values. On the other hand, trigger is a stored procedure that runs automatically when various events happen (eg update, insert, delete).
What are the disadvantages of trigger?
Disadvantages of a trigger are as follows: – Triggers can execute every time some field in database is updated. If a field is likely to be updated often, it is a system overhead. – Viewing a trigger is difficult compared to tables, views stored procedures. – It is not possible to track or debug triggers.
Why we should not use triggers in SQL?
Triggers are 35% faster With OUTPUT, you have more control on the code, because you can extract the inserted and deleted rows in a specific stored procedure whenever you want. The problem with triggers is that they are executed even if you do not want them to.