I have an application that uses a table that has around 25 columns. The app was poorly designed and the table really needs to be broken up into multiple tabes but unfortunatly I can't do that right now. The table has about 700,000 rows in it.

Anyway there are currently 40 indexes on the table. The indexes have various column combinations. Performance on this table is horrible(selects especially). There are a lot of inserts and updates happening. I am wondering... Are there too many indexes on the table? Can there be too many indexes? Especially since indexes are updated on inserts, updates, and deletes?

I thought I heard someone say one time that it would be better to have a single index for each column? I could be off on that. Just looking for some clarification and information on indexes?