Why Trigger Is Used In Database?

Why we use triggers in SQL?

A trigger is a special type of stored procedure that automatically runs when an event occurs in the database server.

DML triggers run when a user tries to modify data through a data manipulation language (DML) event.

DML events are INSERT, UPDATE, or DELETE statements on a table or view..

What is trigger with example?

Trigger: A trigger is a stored procedure in database which automatically invokes whenever a special event in the database occurs. For example, a trigger can be invoked when a row is inserted into a specified table or when certain table columns are being updated.

What is trigger and its types?

Types of triggers A trigger defines a set of actions that are performed in response to an insert, update, or delete operation on a specified table. When such an SQL operation is executed, the trigger is said to have been activated. Triggers are optional and are defined using the CREATE TRIGGER statement.

How do you write a trigger?

Creating TriggersCREATE [OR REPLACE] TRIGGER trigger_name − Creates or replaces an existing trigger with the trigger_name.{BEFORE | AFTER | INSTEAD OF} − This specifies when the trigger will be executed. … {INSERT [OR] | UPDATE [OR] | DELETE} − This specifies the DML operation.More items…

What are cursors in SQL?

A cursor holds the rows (one or more) returned by a SQL statement. The set of rows the cursor holds is referred to as the active set. You can name a cursor so that it could be referred to in a program to fetch and process the rows returned by the SQL statement, one at a time.

What are SQL functions?

A function is a set of SQL statements that perform a specific task. … Next time instead of rewriting the SQL, you can simply call that function. A function accepts inputs in the form of parameters and returns a value. SQL Server comes with a set of built-in functions that perform a variety of tasks.

What is triggers in DBMS?

Triggers are the SQL statements that are automatically executed when there is any change in the database. The triggers are executed in response to certain events(INSERT, UPDATE or DELETE) in a particular table.

What is the main purpose of triggers in database?

Triggers help the database designer ensure certain actions, such as maintaining an audit file, are completed regardless of which program or user makes changes to the data. The programs are called triggers since an event, such as adding a record to a table, fires their execution.

What are the uses of trigger?

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)Write to other files for audit trail purposes.Query from other files for cross-referencing purposes.More items…

Why use a trigger instead of a constraint?

While constraints prevent updates that violate referential integrity, triggers perform explicit actions in addition to the update operation. Triggers can do much more than enforce referential integrity. Because they are passive, constraints are limited to preventing updates in a narrow set of conditions.

What is trigger explain?

A trigger is a block of code that is executed automatically from a database statement. Triggers is generally executed for DML statements such as INSERT, UPDATE or DELETE. It resides in a database code and is fired automatically when the database code requires to perform the INSERT ,UPDATE or DELETE statement.

What are the different types of trigger?

Types of Triggers in OracleDML Trigger: It fires when the DML event is specified (INSERT/UPDATE/DELETE)DDL Trigger: It fires when the DDL event is specified (CREATE/ALTER)DATABASE Trigger: It fires when the database event is specified (LOGON/LOGOFF/STARTUP/SHUTDOWN)

What is trigger in SQL and types?

The SQL Server trigger is a special type of stored procedures that is automatically executed when an event occurs in a specific database server. … The DDL triggers will be fired in response to different Data Definition Language (DDL) events, such as executing CREATE, ALTER, DROP, GRANT, DENY, and REVOKE T-SQL statements.