Index - Advantage and Disadvantage.

 Advantage:

1. Faster retrieval. But in case of NON CLUSTERD INDEX, if the query is around the indexing key like employee(Name) indexing can benefit but if the query is not around Name column the index table is not used and natural table scan is used.

Disadvantage:

1. Additional Disk space- Non Clusted

2. Insert Update and delete will be slow.

3.covering querry .. i.e we have discussed this in advantage point no. 1

4.clusted index always covers querry. i.e advantage point 1 . therefore is superior to non clusted index .