Strange Locking Behaviour in SQL Server 2005

Question

Can anyone please tell me why does the following statement inside a given stored procedure returns repeated results even with locks on the rows used by the first SELECT statement?

BEGIN TRANSACTION DECLARE @Temp TABLE ( ID INT ) INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue <= 10 INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue >= 5 SELECT * FROM @Temp COMMIT TRANSACTION

Any values in SomeTable for which SomeValue is between 5 and 10 will be returned twice, even though they were locked in the first SELECT. I thought that locks were in place for the whole transaction, and so I wasn't expecting the query to return repeated results. Why is this happening?

Community · Accepted Answer · 2017-05-23 11:55:38Z

In the same session/transaction, READPAST won't have any effect.

So even though you have ROWLOCK and UPDLOCK for the first SELECT , the next SELECT ignores these. If the 2nd SELECT was a different session, then it'd work as expected.

See these for more info: ORDER BY and WITH(ROWLOCK, UPDLOCK, READPAST) and TABLOCKX versus SERIALIZABLE

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