Question

Consider the following SQL:

 BEGIN TRAN SET TRANSACTION ISOLATION LEVEL READ COMMITTED  INSERT Bands     (  Name  ) SELECT 'Depeche Mode' UNION SELECT 'Arcade Fire'      -- I've indented the inner transaction to make it clearer.      BEGIN TRAN     SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED      SELECT *       FROM Bands      COMMIT  -- What is the isolation level right here?  UPDATE Bands    SET Name = 'Modest Mouse'  WHERE Name = 'Oddest House'  COMMIT 

In sum, we start a transaction and set its isolation level to READ COMMITTED. We then do some random SQL and start another, nested transaction. In this transaction we change the isolation level to READ UNCOMMITTED. We then commit that transaction and return to the other.

Now, my guess is that after the inner commit, the isolation level returns to READ COMMITTED. Is this correct?

Answer 1

I don’t think that is correct.

Refer to the remarks here: Set Transaction

Only one of the isolation level options can be set at a time, and it remains set for that connection until it is explicitly changed.