What @@ are for in variables?

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What @@ are for in variables?

Mithrandir

SSCrazy

Points: 2628

January 12, 2005 at 4:11 pm

#59886

Hello.

Looking into the Trigger BOL help I realized into one example that uses @@VarName

CREATE TRIGGER employee_insupd
ON employee
FOR INSERT, UPDATE
AS
/* Get the range of level for this job type from the jobs table. */
DECLARE @@MIN_LVL tinyint,
   @@MAX_LVL tinyint,
   @@EMP_LVL tinyint,
   @@JOB_ID smallint
SELECT @@MIN_LVl = min_lvl, 
   @@MAX_LV = max_lvl, 
   @@ EMP_LVL = i.job_lvl,
   @@JOB_ID = i.job_id
FROM employee e, jobs j, inserted i 
WHERE e.emp_id = i.emp_id AND i.job_id = j.job_id
IF (@@JOB_ID = 1) and (@@EMP_lVl <> 10) 
BEGIN
   RAISERROR ('Job id 1 expects the default level of 10.', 16, 1)
   ROLLBACK TRANSACTION
END
ELSE
IF NOT @@ EMP_LVL BETWEEN @@MIN_LVL AND @@MAX_LVL)
BEGIN
   RAISERROR ('The level for job_id:%d should be between %d and %d.',
      16, 1, @@JOB_ID, @@MIN_LVL, @@MAX_LVL)
   ROLLBACK TRANSACTION
END

What are @@ for? What's the difference between using a single @?

I've benn looking in BOL, but can't find anything helpful

Thanks

Viewing 4 posts - 1 through 4 (of 4 total)

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Sopheap Suy SSCertifiable Points: 7893 More actions · Answer 1

@@ is a global value

@ is a local value exist only on that connection.

mom

Mithrandir SSCrazy Points: 2628 More actions · Answer 2

Thanks, I suspected that.

And in the example, what are the benefits of using global variables instead of using local ones?

Ariadne SSCrazy Points: 2044 More actions · Answer 3

Not specifically for this example, but the only benefit I've ever known for a Global Variable is if you have multi processes which need to know what that variable is at that particular given moment, regardless of what processes you have running. It stays up and available to other connections. Since I want full control of what the variable is at all times, then I only use local variables. I suppose if I didn't want to pass a variable value to a nested sproc, then I could use a global, but I'd rather pass the value in the exec statement.