How to Use Event Triggers in SQL Server

How do I create and use event triggers in SQL Server?

An event trigger runs predefined T-SQL code automatically when specific server-level or database-level events occur, such as DDL changes, logons, or error messages.

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Description

What problems do event triggers solve?

Event triggers automate auditing, enforce naming conventions, block unwanted schema changes, and log suspicious logons without relying on application code. They centralize control at the database or server scope.

How do I create a database-level event trigger?

Use CREATE TRIGGER ON DATABASE FOR event_group. Common event groups include DDL_DATABASE_LEVEL_EVENTS and DDL_TABLE_EVENTS.The trigger body contains T-SQL that executes after the event fires.

Example: Audit table changes

This trigger writes a row to AuditLog whenever a table is created or altered. It helps track schema drift in production environments.

CREATE TRIGGER trg_AuditTables ON DATABASE FOR DDL_TABLE_EVENTS AS INSERT INTO AuditLog(event_type, object_name, occured_at) SELECT EVENTDATA().value('(/EVENT_INSTANCE/EventType)[1]', 'nvarchar(100)'), EVENTDATA().value('(/EVENT_INSTANCE/ObjectName)[1]', 'nvarchar(256)'), SYSDATETIME(); GO

How do I create a server-level event trigger?

Prepend ALL SERVER to scope.Typical use cases: blocking risky logons or capturing CREATE DATABASE events for governance.

Example: Prevent unauthorized logins

CREATE TRIGGER trg_BlockTestLogins ON ALL SERVER FOR LOGON AS IF ORIGINAL_LOGIN() = 'test' ROLLBACK; GO

Can I use event triggers with transactional tables?

Event triggers target meta-events, not row-level changes. Pair them with AFTER INSERT/UPDATE/DELETE DML triggers to cover data events on Customers, Orders, Products, and OrderItems.

Best practices for event triggers

Keep trigger bodies short; call stored procedures for complex logic. Always include TRY…CATCH to handle errors.Monitor sys.server_triggers and sys.trigger_events regularly.

How do I disable or drop an event trigger?

Disable temporarily with DISABLE TRIGGER, or remove permanently using DROP TRIGGER. Specify ALL SERVER for server-scope triggers or DATABASE for database-scope ones.

Why How to Use Event Triggers in SQL Server is important

How to Use Event Triggers in SQL Server Example Usage


-- Notify admins by email whenever total_amount column is altered in Orders table
CREATE TRIGGER trg_OrdersAmountChange
ON DATABASE
FOR ALTER_TABLE
AS
IF EVENTDATA().value('(/EVENT_INSTANCE/ObjectName)[1]', 'nvarchar(256)') = 'Orders'
   AND EVENTDATA().value('(/EVENT_INSTANCE/TSQLCommand/CommandText)[1]','nvarchar(max)') LIKE '%total_amount%'
BEGIN
    EXEC msdb.dbo.sp_send_dbmail
         @profile_name = 'Ops',
         @recipients   = 'dba@example.com',
         @subject      = 'total_amount altered',
         @body         = 'Investigate recent schema change to Orders.total_amount';
END;
GO

How to Use Event Triggers in SQL Server Syntax


-- Create database-level event trigger
CREATE TRIGGER <trigger_name>
ON DATABASE
FOR { event_type | event_group } [ ,...n ]
AS
    -- T-SQL body
GO

-- Create server-level event trigger
CREATE TRIGGER <trigger_name>
ON ALL SERVER
FOR { event_type | event_group } [ ,...n ]
AS
    -- T-SQL body
GO

-- Common event groups
--   DDL_DATABASE_LEVEL_EVENTS  -- CREATE/ALTER/DROP database objects
--   DDL_TABLE_EVENTS           -- CREATE/ALTER/DROP TABLE
--   LOGON                      -- Each successful logon
-- Parameters
--   <trigger_name>      Unique name in the scope
--   event_type/group    One or more predefined events
--   ON DATABASE|ALL SERVER Scope selector

/* Ecommerce Example: Log stock adjustments */
CREATE TRIGGER trg_LogStockUpdate
ON DATABASE
FOR ALTER_TABLE
AS
IF EVENTDATA().value('(/EVENT_INSTANCE/ObjectName)[1]', 'nvarchar(256)') = 'Products'
BEGIN
    INSERT INTO ProductSchemaChanges(details, changed_at)
    VALUES (EVENTDATA().query('/EVENT_INSTANCE/*').value('.', 'nvarchar(max)'), GETDATE());
END;
GO

Common Mistakes

Using event triggers for row-level data changes. Fix: Use DML triggers (AFTER INSERT/UPDATE/DELETE) on Customers, Orders, Products, and OrderItems instead.
Leaving error handling out of trigger body. Without TRY…CATCH, failures roll back the triggering event. Fix: Wrap logic in TRY…CATCH and log errors to a helper table.