title: What column should the clustered index be put on?
body: <p>Lately, I have been doing some reading on indexes of all types and the main advice is to put the clustered index on the primary key of the table, but what if the primary key actually is not used in a query (via a select or join) and is just put for purely relational purposes, so in this case it is not queried against.  Example, say I have a <code>car_parts</code> table and it contains 3 columns, <code>car_part_id</code>, <code>car_part_no</code>, and <code>car_part_title</code>.  <code>car_part_id</code> is the unique primary key identity column.  In this case <code>car_part_no</code> is unique as well and is most likely <code>car_part_title</code>.  <code>car_part_no</code> is what is most queried against, so doesn't it make sense to put the clustered index on that column instead of <code>car_part_id</code>?  The basics of the question is what column should actually have the clustered index since you are only allowed one of them?</p>