--- title: "Trigger in SQL server" description: "Trigger in SQL serverTriggers:The trigger is a special kind of stored procedure that executes automatically when a user attempts the specified da" author: "Anonymous User" published: 2011-07-18 updated: 2020-06-15 canonical: https://www.mindstick.com/articles/569/trigger-in-sql-server category: "database" tags: ["database"] reading_time: 10 minutes --- # Trigger in SQL server ## Trigger in SQL server ### Triggers: The trigger is a special kind of stored procedure that executes automatically when a user attempts the specified [data-modification statement](https://www.mindstick.com/articles/1391/crud-operation-using-jquery-and-http-handler-ashx-in-asp-dot-net) on the specified table (like insert, update, delete query, etc.).A Trigger is a block of code, fired whenever data in the underlying table is affected by any of the Data Manipulation Language (DML) statements in the SQL server. The difference between a Trigger and a Stored Procedure is that the trigger is former is attached to a table and is only fired when an INSERT, UPDATE or DELETE occurs. And when You specify the modification action’s that fire the trigger when it is created. **There are many types of trigger available in SQL server in which some important trigger is given as follows:** - DML Trigger - DDL Trigger - Logon Trigger ##### DML Trigger: A trigger is a special kind of stored procedure that automatically executes when an event occurs in the database server. DML triggers execute 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. These triggers fire when any valid event is fired, regardless of whether or not any table rows are affected. ##### AFTER Trigger for INSERT event: When trigger fired on insert event on any table then it is called a Trigger for ‘Insert’. ##### Syntax: ``` ----- SYNTAX DEMONSTRATION OF TRIGGER ON INSERT EVENT ON ANY TABLE----CREATE TRIGGER OR ON INSERTAS---TRIGGER BODY OR EXECUTION CODE WHICH WANT TO EXECUTE-----GO ``` ##### Example: Creating Trigger on AFTER Insert Event ``` ------DEMONSTRATION OF CREATING TRIGGER ON INSERT EVENTCREATE TRIGGER INSERT_TRIGGERON USERLOGININFOAFTER INSERTASPRINT 'INSERT TRIGGER EXECUTED AFTER INSERT VALUE INTO TABLE'GO ``` ##### AFTER Trigger for Update Event: When trigger fired on insert event on any table then it is called Trigger for ‘Update’. ##### Syntax: Creating Trigger for AFTER Update event ``` ----- SYNTAX DEMONSTRATION OF TRIGGER ON UPDATE EVENT ON ANY TABLE----CREATE TRIGGER OR ON  UPDATEAS---TRIGGER BODY OR EXECUTION CODE WHICH WANT TO EXECUTE-----GO ``` ##### Example: Creating Trigger on AFTER Update Event ``` ---- DEMONSTRATION FOR CREATING TRIGGER FOR UPDATE EVENT ON TABLECREATE TRIGGER UPDATE_TRIGGERON USERLOGININFOAFTER UPDATEASPRINT ‘UPDATE TRIGGER EXECUTED AFTER INSERT VALUE INTO TABLE'GO ``` ##### AFTER Trigger for Delete Event: When trigger fired on insert event on any table then it is called a Trigger for ‘Update’. ##### Syntax: Creating Trigger for AFTER Delete event ``` ----- SYNTAX DEMONSTRATION OF TRIGGER ON DELETE EVENT ON ANY TABLE----CREATE TRIGGER OR ON DELETEAS---TRIGGER BODY OR EXECUTION CODE WHICH WANT TO EXECUTE-----GO ``` ##### Example: Creating Trigger on AFTER DELETE Event ``` ---- DEMONSTRATION FOR CREATING TRIGGER FOR DELETE EVENT ON TABLECREATE TRIGGER DELETE_TRIGGERON USERLOGININFOAFTER DELETEASPRINT DELETE TRIGGER EXECUTED AFTER INSERT VALUE INTO TABLE'GO ``` ##### DDL Trigger: DDL triggers execute in response to a variety of data definition language (DDL) events. These events primarily correspond to Transact-SQL CREATE, ALTER, and DROP statements, and certain system stored procedures that perform DDL-like operations. ##### Trigger for Create Table: ##### Syntax: Creating DDL Trigger for CREATE table into the database ``` ---- SYNTAX DEMONSTRATION TO CREATING DDL TRIGGER FOR CREATING TABLE INTO DATABASECREATE TRIGGER ON DATABASEFOR CREATE_TABLEAS---SQL EXECUTABLE CODE FOR CREAT TABLE EVENT---GO ``` ##### Example: Creating DDL Trigger for CREATE table into the database ``` ----DEMONSTRATION TO CREATING DDL TRIGGER FOR CREATING TABLE INTO DATABASECREATE TRIGGER CREATE_TABLEEON DATABASEFOR CREATE_TABLEASPRINT 'TRIGGER FOR CREATE TABLE IN DATABASE'GO ``` ##### The trigger for Drop Table: ##### Syntax: Creating DDL Trigger for DROP table into the database ``` ---- SYNTAX DEMONSTRATION TO CREATING DDL TRIGGER FOR DROPPING TABLE INTO DATABASECREATE TRIGGER ON DATABASEFOR DROP_TABLEAS---SQL EXECUTABLE CODE FOR DROP TABLE EVENT---GO ``` ##### Example: Creating DDL Trigger for DROP table into database ``` ----DEMONSTRATION TO CREATING DDL TRIGGER FOR DROP TABLE INTO DATABASECREATE TRIGGER DROP_TABLEEON DATABASEFOR DROP_TABLEASPRINT 'TRIGGER FOR DROP TABLE IN DATABASE'GO ``` ##### Trigger for Alter Table: ##### Syntax: Creating DDL Trigger for ALTER table into database ``` ---- SYNTAX DEMONSTRATION TO CREATING DDL TRIGGER FOR ALTERING TABLE INTO DATABASECREATE TRIGGER ON DATABASEFOR ALTER_TABLEAS---SQL EXECUTABLE CODE FOR ALTER TABLE EVENT---GO ``` ##### Example: Creating DDL Trigger for ALTER table into database ``` ----DEMONSTRATION TO CREATING DDL TRIGGER FOR ALTER TABLE INTO DATABASECREATE TRIGGER ALTER_TABLEEON DATABASEFOR ALTER_TABLEASPRINT 'TRIGGER FOR ALTER TABLE IN DATABASE'GO ``` ##### Logon Trigger: Logon Trigger event is raised when a user session is established with an instance of SQL Server. Logon triggers fire after the authentication phase of logging in finishes, but before the user session is actually established. Therefore, all messages originating inside the trigger that would typically reach the user, such as error messages and messages from the PRINT statement, are diverted to the SQL Server error log. Logon triggers do not fire if authentication fails. ##### Syntax: Creating LOGON Trigger into database ``` -----SYNTAX DEMONSTRATION OF CREATING LOGON TRIGGERCREATE TRIGGER ON ALL SERVER FOR LOGONAS--- SQL QUERY TO RETRIEVE INFORMATION OR STORED INFORMATIONGO ``` ##### Example: Creating LOGON Trigger into database ``` ---- CREATE NEW DATABASE TO STORE TRIGGER CREATE DATABASE LOGON_TRIGGER  ---- CREATE TABLE USING ABOVE DATABASE USE LOGON_TRIGGER----TABLE WHICH STORED LOGIN INFORMATION OF LOGIN SQL SERVER USERCREATE TABLE LOGIN_USER(  SYSTEMUSER VARCHAR(50),  DATABASEUSER VARCHAR(50),  LOGTIME DATETIME)   -----DEMONSTRATION OF LOGON TRIGGER  CREATE TRIGGER LOGON_TRIGGERRON ALL SERVER FOR LOGONASINSERT INTO LOGON_TRIGGER.dbo.LOGIN_USER VALUES (SYSTEM_USER,USER,GETDATE())GO ``` ##### Instead Of Trigger in SQL Server: AFTER triggers do not work for views, so we will discuss the properties and functionality of INSTEAD OF triggers. 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. Inserted and deleted tables are widely used in operations inside triggers. INSTEAD OF triggers give you the ability to evaluate the changes that would have taken place if the data modification statement had actually executed. Like AFTER triggers, each INSTEAD OF trigger gives you access to two virtual tables called Inserted and Deleted. For a DELETE trigger, the virtual table Deleted holds all the deleted rows, and for an INSERT trigger, the virtual table Inserted holds all the new rows. An UPDATE trigger populates both the Inserted and Deleted tables; the Deleted table stores the old version of the rows, and the Inserted table stores the new version. An UPDATE trigger populates both the Inserted and Deleted tables; the Deleted table stores the old version of the rows, and the Inserted table stores the new version. **Basically there are three types of Instead Of Trigger in SQL server which are namely define as follows:** - Instead Of Insert Trigger - Instead Of Update Trigger - Instead Of Delete Trigger ##### Instead Of Insert Trigger: INSTEAD OF INSERT triggers can be defined on a view or table to replace the standard action of the INSERT statement. Usually, the INSTEAD OF INSERT trigger is defined on a view to insert data into one or more base tables. ##### Syntax: Creating Instead Of Insert Trigger ``` -----SYNTAX DEMONSTRATION OF INSTEAD OF INSERT TRIGGER--CREATE TRIGGER ON OR INSTEAD OF INSERT ASBEGIN----INSERT SQL QUERY TO INSERT DATA INTO TABLE----TRIGGER BODY SQL CODE---ENDGO ``` ##### Example: Creating Instead Of Insert Trigger ``` ----CREATE VIEW FOR DEMONSTRATION OF CREATING INSTEAD OF INSERT TRIGGER CREATE VIEW TEST_INSERT_INSTEADOF AS SELECT * FROM Userlogin ------DEMONSRATION OF CREATING INSTEAD OF INSERT TRIGGER--  CREATE TRIGGER TEST_INSTEADOF_TRIGGER  ON TEST_INSERT_INSTEADOF  INSTEAD OF INSERT  AS  INSERT INTO Userlogin  SELECT * FROM INSERTED  GO ``` ##### Instead of Delete Trigger: INSTEAD OF DELETE triggers can be defined on a view or table to replace the standard action of the DELETE statement. Usually, the INSTEAD OF DELETE trigger is defined on a view to modify data in one or more base tables. DELETE statements do not specify modifications to existing data values. DELETE statements specify only the rows that are to be deleted. ##### Syntax: Creating Instead of Delete Trigger ```   -----SYNTAX DEMONSTRATION OF INSTEAD OF DELETE TRIGGER--CREATE TRIGGER ON OR INSTEAD OF DELETE ASBEGIN----DELETE SQL QUERY TO INSERT DATA INTO TABLE----TRIGGER BODY SQL CODE---ENDGO ``` ##### Example: Creating Instead of Delete Trigger ``` ----CREATE VIEW FOR DEMONSTRATION OF CREATING INSTEAD OF DELETE TRIGGER CREATE VIEW TEST_DELETE_INSTEADOF AS SELECT * FROM Userlogin ------DEMONSRATION OF CREATING INSTEAD OF DELETE TRIGGER--  CREATE TRIGGER TEST_INSTEADOF_TRIGGER  ON TEST_DELETE_INSTEADOF  INSTEAD OF DELETE  AS  INSERT INTO Userlogin  SELECT * FROM DELETEED  GO ``` ##### Instead of Update Trigger: INSTEAD OF UPDATE triggers can be defined on a view or table to replace the standard action of the UPDATE statement. Usually, the INSTEAD OF UPDATE trigger is defined on a view to modify data in one or more base tables. UPDATE statements that reference views with INSTEAD OF UPDATE triggers must supply values for all non null view columns referenced in the SET clause. ##### Syntax: Creating Instead of Update Trigger ```   -----SYNTAX DEMONSTRATION OF INSTEAD OF UPDATE TRIGGER--CREATE TRIGGER ON OR INSTEAD OF UPDATE ASBEGIN----UPDATE SQL QUERY TO INSERT DATA INTO TABLE----TRIGGER BODY SQL CODE---ENDGO ``` ##### Example: Creating Instead of Update Trigger ``` ----CREATE VIEW FOR DEMONSTRATION OF CREATING INSTEAD OF UPDATE TRIGGER CREATE VIEW TEST_UPDATE_INSTEADOF AS SELECT * FROM Userlogin ------DEMONSRATION OF CREATING INSTEAD OF UPDATE TRIGGER--  CREATE TRIGGER TEST_INSTEADOF_TRIGGER  ON TEST_UPDATE_INSTEADOF  INSTEAD OF DELETE  AS  UPDATE Userlogin SET Id = deleted.id, Name = deleted.name      GO ``` ##### Magic Table: In SQL server magic table is nothing more than an internal table which is created by the SQL server to recover recently inserted, deleted and updated data into SQL server database. Basically there are two types of magic table in SQL server namely: inserted and deleted, update can be performed with help of these twos. Generally we cannot see these two table, we can only see it with the help Trigger’s in SQL server. Let’s see the following example: ##### INSERTED Magic Table: When we insert record into table then ‘inserted’ magic table are created and recently inserted record are available in this table we can access this record with the help of Trigger’s. Let’s see the demonstration of inserted magic table. ##### Example: ``` --- CREATE TABLE TO DEMONSTRATION OF INSERT MAGIC TABLE ----CREATE TABLE INSERT_MAGIC(ID INT,TRIGGER_MESSAGE VARCHAR(50) ) -------DEMONSTRATION OF CREATING TRIGGER TO EXPLORE INSERTED MAGIC TABLE   CREATE TRIGGER TRI_MAGIC_INSERT  ON USERLOGIN  INSTEAD OF INSERT  AS  BEGIN  DECLARE @ID INT  SELECT @ID = (SELECT ID FROM inserted)  INSERT INTO INSERT_MAGIC VALUES (@ID,'RECORD ADDED')  END  GO ``` ##### Note:Here ‘inserted’ is insert magic table ##### DELETED Magic Table: When we delete record from the table then SQL automatically create a deleted magic table which holds are deleted data from actual table if we want to recover it then we can access that data from deleted magic table. Let’s see demonstration of recover data from deleted magic table. ##### Example: Creating Trigger for Deleted Magic table ``` -------DEMONSTRATION OF CREATING TRIGGER TO EXPLORE INSERTED MAGIC TABLE   CREATE TRIGGER TRI_MAGIC_DELETE  ON USERLOGIN  INSTEAD OF INSERT  AS  BEGIN  DECLARE @ID INT  DECLARE @NAME VARCHAR(50)  SELECT @ID = (SELECT ID FROM deleted)  SELECT @NAME = (SELECT NAME FROM deleted)  INSERT INTO INSERT_MAGIC VALUES (@ID,@NAME)  END  GO ``` ##### You can also read these related post [https://www.mindstick.com/Articles/330/triggers-in-sql-server](https://www.mindstick.com/Articles/330/triggers-in-sql-server)[https://www.mindstick.com/Articles/1299/trigger-in-sql-server](https://www.mindstick.com/Articles/1299/trigger-in-sql-server) --- Original Source: https://www.mindstick.com/articles/569/trigger-in-sql-server Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.