In general, is it better from a query performance perspective (I'm not particularly concerned about disk space) to have one index on multiple columns, or to create individual indexes for each column needed in queries?

My specific issue is with a table of appx. 100K rows and 15 columns. 9 of those columns I think should have an index on them as they'll be used for various queries (usually no more than 2 or 3 at a time though).

I'm concerned that if I make one or two multi-column indexes, many times they won't be used for the query. However, having a 15 column table with 9 indexes also seems rather odd.

I'm more interested in a "general" discussion and not necessarily specific to my current concern. This is an extreme case but I've pondered this on other tables in the past.