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What happens when you drop an index in SQL Server?
By disabling an index, you have basically turned off the index, but have allowed SQL Server to retain the index definition in the database metadata. If you want the index back all you need to do is rebuild the index. If you drop the index, SQL Server no longer retains the metadata for the index.
Why are you dropping and Recreating Your indexes?
It is common practice to drop indexes and then create them to optimize the data load process. By not having the indexes at load time SQL Server can load the data much faster, because there are no indexes to update. This is a common practice for optimizing loading large data warehouse table loads.
How to get rid of unused Index in SQL Server?
Make sure you don’t have index hints before you make any changes to an index. You can find the query to find index hints here or start with this script: Test. Test. Test. Test how long a query using “unused” index is running with the index. Test how long a query using “unused” index is running without the index.
When to delete or disabling ” unused ” indexes can cause application issues?
Here is another real-life example when deleting or disabling “unused” indexes can cause application issues. If a vendor’s application queries have table/query hints to force a specific index usage you will break the application by dropping this index. Here is an error the application will raise:
Table locks are applied and the table is unavailable for the duration of the index operation. The ONLINE option can only be specified when you drop clustered indexes. For more information, see the Remarks section. Online index operations are not available in every edition of SQL Server.
Can a SQL query return the same result every time?
The ORDER BY clause contains a column or combination of columns that are guaranteed to be unique. Although this specifically refers to offset / fetch, it clearly applies to running the query multiple times without those clauses. The result is everytime the same when you are in a single-threaded environment.
How to return results in 10 row increments?
For example, to return the results of a query in 10-row increments, you must execute the query one time to return rows 1 to 10 and then run the query again to return rows 11 to 20 and so on. Each query is independent and not related to each other in any way.
Can a stable sort query return the same result?
In contrast, a query with stable sort ( ordering also by Id) should always return the same results, since ID s are unique: The question is: Is my intuition correct? If yes, can you provide an actual example of operations that would produce different results (at least “on your machine”)?