title: Is the query processing fast if I create an index on a column but make a query for multiple column out of which one is the indexed column?
body: <p>For example, let's say I created index on <code>'id'</code> but I make a query like this:</p>
  
  <pre><code>select id, class, name from student;
  </code></pre>
  
  <p>Will the query processing be random or will it be optimised according to the id column?</p>