Can 2 tables cause a deadlock, if the pagelocks are off, and the rows are not related. E.g.
Query 1 runs for a few seconds
Select * from Orders where CustomerID = 1 and DateOrdered between @D1 and @D2
Query 2 starts to run, and ends, before Query 1 is finished, but with a different customerID
Update Orders set Quantity = Quantity + 10 where OrderID = 20 and CustomerID = 2
(These are just examples to prove a point please)
Now there is a PK_Orders which is a clustered index on the OrderID. There is also a separate index (ix_Order_Customer) which is a non-clustered index, and contains CustomerID as one of the fields to index. This index has pagelocks enabled.
What I don't understand is how SQL (with traceID 1222) showed me in SQL Server logging that the PK_Orders caused a deadlock when the query which was executed did not even affect the same OrderIDs which were updated.
Extract from Log File Viewer:
keylock hobtid=720229632 dbid=5 objectname=myDB.dbo.Orders indexname=PK_Orders id=lock1b0b23c0 mode=X associatedObjectId=720229632
pagelock fileid=1 pageid=195848 dbid=5 objectname=myDB.dbo.Orders id=lock24442a40 mode=S associatedObjectId=720229274
Can someone help explain how this is possible please, should the Deadlock not only kick in if there were intersecting rows here? I copied the 2 queries and ran them at the same time, yet I cannot recreate the error and in SQL Server Management Studio this error does not occur - the update goes through.
The error in SQL Event Log Viewer specifically says that PK_Orders is the cause here.