so you are going to explain "multi-column indexes"
i have some questions:
1. what's the absolute vantage for multi rather than single column index
2. can u explain it on some sample table? e.g.: on Forum/Post table, or Category/Products table, this is more common used table struct IMHO
3. and tell us what situation we should/shouldn't use it
4. and what else should we take care of to do the best optimize
5. when will your plan be done, and where to get it? here?