One of the Oracle databases I work with has an index on a table that spans 6 attributes. Someone now wants to create another index on the same table that is comprised of 3 of the attributes that are part of the first index.
Does that make any sense? How can that be helpful, couldn't the db simply use the first index to get the performance benefit they are looking for? I'm puzzled by this but don't want to object if there is actually a good reason for doing this.