SQL SERVER

 DML Triggers  DDL Trigers

 INSERT triggers  DELETE triggers  UPDATE triggers  A mix and match of any of the above

 ALTER TRIGGER TriggerOne ON Person  AFTER UPDATE AS  SELECT D.LastName + ‘ changed to ’ + I.LastName  FROM Inserted AS I  INNER JOIN Deleted AS D  ON I.PersonID = D.PersonID;  GO  UPDATE Person  SET LastName = ‘Carter’  WHERE LastName = ‘Johnson’;  Result:   Johnson changed to Carter  (2 row(s) affected)

 Your business rule needs to reference data in a separate table.  Your business rule needs to check the delta (difference between before and after) of an UPDATE.  You require a customized error message.  Using Triggers for Custom Error Messages  Updating summary information  Feeding de-normalized tables for reporting  Setting condition flags

 Complex data validation  Writing data-audit trails  Maintaining modified date columns  Enforcing custom referential-integrity checks and cascading deletes

 CREATE TRIGGER Sales.SalesOrderDetailNotDiscontinued  ON Sales.SalesOrderDetail  FOR INSERT, UPDATE AS  IF EXISTS(  SELECT ‘True’ FROM Inserted i  JOIN Production.Product p ON i.ProductID = p.ProductID  WHERE p.DiscontinuedDate IS NOT NULL)  BEGIN  RAISERROR(‘Order Item is discontinued. Transaction Failed.’,16,1)  ROLLBACK TRAN  END

 UPDATE Production.Product  SET DiscontinuedDate = ‘ ’  WHERE ProductID = 680  INSERT INTO Sales.SalesOrderDetail  VALUES  (43659, ‘ C-98’, 1, 680, 1, ,0.00, NEWID(), GETDATE())

 Msg 50000, Level 16, State 1, Procedure SalesOrderDetailNotDiscontinued, Line 14  Order Item is discontinued. Transaction Failed.  Msg 3609, Level 16, State 1, Line 1  The transaction ended in the trigger. The batch has been aborted.

 CREATE TRIGGER  ON [.]  [WITH ENCRYPTION | EXECUTE AS >]  {{{FOR|AFTER} } |INSTEAD OF}  [WITH APPEND]  [NOT FOR REPLICATION]  AS  | EXTERNAL NAME >

 CREATE TRIGGER Production.ProductIsRationed  ON Production.ProductInventory  FOR UPDATE AS IF EXISTS(  SELECT ‘True’ FROM Inserted i  JOIN Deleted d ON i.ProductID = d.ProductID  AND i.LocationID = d.LocationID  WHERE (d.Quantity - i.Quantity) > d.Quantity / 2  AND d.Quantity – i.Quantity > 0)  BEGIN  RAISERROR(‘Cannot reduce stock by more than 50% at once.’,16,1)  ROLLBACK TRAN  END

 ALTER TABLE  TRIGGER >

 =] ‘ ’,  =] ‘{FIRST|LAST|NONE}’,  =] ‘{INSERT|UPDATE|DELETE}’  [, =] {‘DATABASE’ | ‘SERVER’ | NULL} ]

 Controlling Firing Order for Logic Reasons  Controlling Firing Order for Performance Reasons

EXEC sp_configure ‘Nested Triggers’, 0; RECONFIGURE;

 ALTER DATABASE DatabaseName SET RECURSIVE_TRIGGERS ON | OFF ;

 Keep It Short and Sweet  Don’t Forget Triggers When Choosing Indexes  Try Not to Roll Back Within Triggers

 DROP TRIGGER [.]

 CREATE, ALTER, or DROP database  RESTORE database or log

 ALTER TRIGGER Production.ProductIsRationed  ON Production.ProductInventory  FOR UPDATE AS  IF UPDATE(Quantity)  BEGIN  IF EXISTS(  SELECT ‘True’  FROM Inserted i  JOIN Deleted d  ON i.ProductID = d.ProductID  AND i.LocationID = d.LocationID  WHERE (d.Quantity - i.Quantity) > d.Quantity / 2  AND d.Quantity > 0 )  BEGIN  RAISERROR(‘Cannot reduce stock by more than 50% at once.’,16,1)  ROLLBACK TRAN  END

 | Represents bitwise OR  & Represents bitwise AND  ^ Represents bitwise Exclusive OR