title: Is there any harm in creating a index that is a subset of unique clustered index?
body: <p>I have a table <code>ABC</code> and a unique clustered index on below columns</p>
  
  <pre><code>col1, col2, col4, col5, col6
  </code></pre>
  
  <p>It's a vast table and analyzing most of the queries on this table I feel that a new index of below columns would help.</p>
  
  <pre><code>col1, col5, col2
  </code></pre>
  
  <p>But, I am not sure of the performance impact and need to know whether it;s a good idea to create this additional index. So, basically can we have a index that has columns that are subset of a unique clustered index (also with order changed)? </p>
  
  <p>Haven't found anything related while searching internet. Any hint's/thoughts would be helpful.</p>