title: Do clustered indexes have to be unique?
body: <p>What happens if a clustered index is not unique? Can it lead to bad performance because inserted rows flow to an &quot;overflow&quot; page of some sorts?</p>
  <p>Is it &quot;made&quot; unique and if so how? What is the best way to make it unique?</p>
  <p>I am asking because I am currently using a clustered index to divide my table in logical parts, but the performance is so-so, and recently I got <a href="https://stackoverflow.com/questions/3733735/clustered-indexes-on-non-identity-columns-to-speed-up-bulk-inserts/4331661#4331661">the advice</a> to make my clustered indexes unique. I'd like a second opinion on that.</p>