Why Covering Index is better than creating several non-clustered index?

 Posted by Rajnilari2015 on 3/16/2016 | Category: Sql Server Interview questions | Views: 214 | Points: 40
Answer:

Instead of creating several non-clustered index, try using Covering Index because it can satisfy all requested columns in a query without performing a further lookup into the clustered index.If all the columns requested in the select list of query, are available in the index, then the query engine doesn't have to lookup the table again which can significantly increase the performance of the query. Since all the requested columns are available with in the index, the index is covering the query. It enhances the query performance by avoiding unnecessary lookups.


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