SQL Server and Over-Indexing Tables Possible Duplicate:
  Where can I find some guidance on index strategies?  




I remember taking a course on SQL Server 2000, and the instructor said that you have to be careful of adding too many indexes to a table, because this can lead to performance problems with querying from the table.  With the release of SQL Server 2012, are these kinds of problems still a concern?
Yes, of course. Every index you create requires maintenance (it needs to be updated for every insert, update and delete operation) and occupies space. Indexes aren't free performance boosts, and should certainly be considered as a trade-off. You should also be very careful about throwing an index on a table to satisfy one query that is called once a week if that table is written all week long. In other words, don't look at the missing index DMVs or a single execution plan and judge the validity of a suggested index in isolation.