Where is non-clustered index used?
A non-clustered index is also used to speed up search operations. Unlike a clustered index, a non-clustered index doesn’t physically define the order in which records are inserted into a table. In fact, a non-clustered index is stored in a separate location from the data table.
When a table does not have a clustered index the query will end up performing which type of execution?
The interesting thing, alluded to previously, is that when you don’t have a clustered index you will end up with table scan which means you will have the same logical reads no matter how big the result you are selecting is. So, it will be much better if you have created a clustered index.
How does clustered index seek work in SQL Server?
If I move to the execution plan, you can see the Clustered Index Scan which was in the previous case has been transformed into a Clustered Index Seek, hence SQL Server was able to narrow down, using the clustered index key, to obtain this particular value based on the where condition, which is in the seek predicate
Can a PK be a non unique clustered index?
If not unique then it cannot be a PK, but can still be a non-unique Clustered Index. Then your non-clustered index would be only on the measure column. And, considering that the first field in the GROUP BY is also measure, that would also benefit from having measure be the leading field.
Is it good or bad to use clustered index?
Good or bad: This is the ideal condition. It is generally good to see the Clustered Index Seek Action item: Evaluate the possibility of using a non-clustered index, so that you gain the possibility of eliminating, if required, even the Clustered Index Seek.
Which is better clustered index or table scan?
The interesting thing, alluded to previously, is that when you don’t have a clustered index you will end up with table scan which means you will have the same logical reads no matter how big the result you are selecting is. So, it will be much better if you have created a clustered index. This will be further demonstrated in the next section.