If your analysis shows that more than one column is a good candidate for a clustered index key, you may be able to provide clustered-like access with a composite index that covers a particular query or set of queries. These include:
Range queries.
Vector (grouped) aggregates, if both the grouped and grouping columns are included. Any search arguments must also be included in the index.
Queries that return a high number of duplicates.
Queries that include order by.
Queries that table scan, but use a small subset of the columns on the table.
Tables that are read-only or read-mostly can be heavily indexed, as long as your database has enough space available. If there is little update activity and high select activity, you should provide indexes for all of your frequent queries. Be sure to test the performance benefits of index covering.
