To speed up queries :-)
But it takes its price when you insert/delete big amount of data.

>Maybe a dumb question but why have a clustered index?
>
>>>I am looking to see if there could be a way to optimize a delete SQL I have.
>>>
>>>Basically, I do something like this every 15 minutes:
>>>
>>>

>>>DELETE FROM Hit WHERE AddDate<something
>>>

>>>
>>>As this is executed every 15 minutes, usually, this is executed in a flash. So, all records from the Hit table which are older than the parameter will be removed. The situation is when I run this command on a test server, where this procedure hasn't been executed since a while, the process may take several minutes.
>>>
>>>Is it because I am working on a date field? If yes, I can do a SQL at first to get the primary key and then remove anything older than that primary key.
>>>
>>>Or, is it that it is because there are a lot of records? If this is the case, what can I do to optimize?
>>
>>As I saw from the Execution plat the most part of the operation if for recreating the clustered index.
>>Could you try to remove the index first then DELETE and then recreate it?