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Archive for the ‘Deprecated Features’ Category

Ability to return result sets from triggers is one of the features that is marked as a deprecated feature in SQL Server 2012.
After reading this, few questions flashed my mind, that I would like to share with you.

  • How do we return the result sets from triggers?
  • Why do we need this feature mostly?
  • How can we stop using this feature from earlier versions?
  • How can we get the same functionality without using this feature?

I added first two questions for the beginners to understand this concept.

Lets proceed step by step from the first question.

  • How do we return the result sets from triggers ?

Step 1 :
Lets create a table to demonstrate the use of return the result sets from trigger.

USE tempdb;
GO
CREATE TABLE tbl_Employee(
EmployeeID int identity (1,1),
EmployeeName nvarchar(100) NULL
)
GO

Step 2 :
Create a trigger on this table (tbl_Employee).

CREATE TRIGGER trg_Insert ON tbl_Employee
FOR INSERT
AS
  SELECT INSERTED.EmployeeID, INSERTED.EmployeeName FROM inserted;
GO

Step 3 :
Now, lets insert one record and check if it is working properly.

INSERT INTO tbl_Employee VALUES('Imran')
GO
--OUTPUT

triggerresultset1.1

Woww, it is working, we got the result sets from the trigger 😉

  • Why do we need this feature mostly?

Mostly, we use select statement inside the trigger/ stored procedure to return the result set and the purpose of the result set is to debug (to check what values it returns) the trigger / stored procedure.
(Note : It is a common practice to debug any trigger/stored procedure via result set, but it may break your application and also it is not recommended).

  • How can we stop using this feature from earlier versions?

Step 4 :
We are enabling an advance feature ‘disallow results from triggers’ to 1 to enable this feature in the earlier version of SQL Server and it is also recommended by SQL Server to make it 1.

sp_configure 'disallow results from triggers',1
GO
RECONFIGURE

Step 5 :
Insert one more record in the table after enabling the feature and check that this feature has enabled properly or not.

INSERT INTO tbl_Employee VALUES('Bob')
GO
--OUTPUT

Ooopps…… I am unable to execute it, because I enabled the return result set feature from trigger at instance level not on database level
and it is working fine.
Msg 524, Level 16, State 1, Procedure trg_Insert, Line 4
A trigger returned a resultset and the server option ‘disallow_results_from_triggers’ is true.

  • How can we get the same functionality without using this feature?

Step 6 :
You can easily use the same functionality without using this feature. Let me alter the trigger and make a sample.

ALTER TRIGGER trg_Insert ON tbl_Employee
FOR INSERT
AS

  Declare @EmployeeID int
  Declare @EmployeeName nvarchar(100)

  SELECT @EmployeeID=INSERTED.EmployeeID
  , @EmployeeName=INSERTED.EmployeeName FROM inserted;

  Print 'EmployeeID ' + Convert (varchar(10),@EmployeeID)
  Print 'Employee Name ' + @EmployeeName
GO

Step 7 :
Insert one more record in the table and check the functionality.

INSERT INTO tbl_Employee VALUES('Sandra')
GO
--OUTPUT

EmployeeID 3
Employee Name Sandra

Conclusion :
DO NOT  use SELECT statement to return the result set from a stored procedure / trigger. Always use print command instead, to debug it.

Reference : MSDN

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