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Why is this query not using my nonclustered index?
The first query uses the clustered index, the second query uses my non-clustered index. My question is two parts: Why, since both queries have a WHERE clause on the [DateEntered] field, does the server use the clustered index on the first, but not the second?
What causes a query to exceed the Lock escalation threshold?
This means that what may look like a SELECT statement at a “read-committed” isolation level might acquire many thousands of key locks (on both the clustered index and one nonclustered index). This can cause such a query to exceed the lock escalation thresholds.
How to determine which query took a lock?
This example demonstrates a method of determining what query took the lock, the plan of the query, and the Transact-SQL stack at the time the lock was taken. This example also illustrates how the pairing target is used in an Extended Events session.
How to read clustered index in SQL Server?
It can use the allocation maps to lookup scan ranges and just start reading the Clustered index in large chunks. This is sequential and much cheaper. (as long as your table isn’t fragmented 🙂 ) The downside is, the WHOLE clustered index needs to be read.
Why is SQL Server not using my index?
OK – as long as you select only the column that’s in the index, or something from the clustering key (usually, this is the primary key), then the index will be used, since SQL Server can find all the information it needs (the UserTask_IDEntitat column, and the clustered index column (s) ) in the leaf level of the index navigation structure.
When to use Index on usertask Identitat?
CONSTRAINT [PK_UserTask] PRIMARY KEY CLUSTERED ( [UserTask_ID] ASC ) ON [PRIMARY] ) ON [PRIMARY] Executing the following query, execution plan shows us that index on UserTask_IDEntitat is used to do the query: