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SQL Server 2008R2 Concurrency

Greetings,

      I’m using SQL Server 2008R2 in its default configuration. Below are three skeleton examples of stored procedures.

      Question: How do I ensure that each of these types of stored procedures will run as an atomic operation in a multi threaded environment? Does the default locking ensure that the underlying table cannot change between testing if a value exists and updating that value? Should I always put a TRANSACTION BEGIN / COMMIT TRANSACTION around these types of stored procedures? What’s the best practice approach for handling this?

Thanks,

Karsten

############################################################
STORED PROCEDURE EXAMPLE 1:

IF EXISTS(SELECT * FROM MyTable WHERE MyId = @MyId)
BEGIN
      -- Update
      UPDATE MyTable
      SET
            MyData = @MyData
      WHERE MyId = @MyId
END
ELSE
BEGIN
      -- Insert
      INSERT MyTable
      (
       MyData,
       MyId
      )
      VALUES
      (
            @MyData,
            @MyId
      )
END

############################################################
STORED PROCEDURE EXAMPLE 2:

      DELETE FROM MyTable1 WHERE MyId = @MyId
      DELETE FROM MyTable2 WHERE MyId = @MyId

############################################################
STORED PROCEDURE EXAMPLE 3:

      DECLARE @Test1 bit
      IF EXISTS(SELECT * FROM MyTable MyId = @MyId)
            SET @Test1 = 1
      ELSE
            SET @Test1 = 0

      DECLARE @Test2 bit
      IF EXISTS(SELECT * FROM MyTable MyId = @MyId2)
            SET @Test2 = 1
      ELSE
            SET @Test2 = 0


      DECLARE @CombinedTest int
      SET @CombinedTest = 0
      IF @Test1 = 1 SET @CombinedTest = @CombinedTest + 1
      IF @Test2 = 1 SET @CombinedTest = @CombinedTest + 2

      RETURN @CombinedTest

ASKER CERTIFIED SOLUTION

lcohan

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lcohan

By the way, I think you could re-write the second SP to something like below where you definitely won't need explicit transaction:

select case
      when EXISTS (SELECT * FROM MyTable where MyId = Id1) then 1
      when EXISTS (SELECT * FROM MyTable where MyId = Id2) then 2
      when EXISTS (SELECT * FROM MyTable where MyId = Id1) and EXISTS (SELECT * FROM MyTable where MyId = Id2) then 3
else 0 end

karstenweber

ASKER

Thanks for the feedback Icohan. I did suspect that the default read commited isolation would suffice, but it wasn't exactly clear. Thanks for the re-write. The original form was pretty brain dead, but did show the multiple select that I was concerned about.

Karsten