title: How does index created on separate columns works internally?
body: <p>I have a table Employee which has 10 columns . In my query where clause i am using column1 and column2 . If i create index on both columns
  i.e. column1 and column2 . Is there a possibility both index can be utilized ?</p>
  
  <p>There can be two approaches :- </p>
  
  <ul>
  <li><p>Approach1: For first where clause index is used and for second where
  clause result return by first clause is further filtered without
  using second index</p></li>
  <li><p>Approach2: For first where clause index is used , get row ids. For
  second where clause index is used , get row ids and do intersection
  of both rowIds</p></li>
  </ul>
  
  <p>How does index works here ?</p>
  
  <p><strong>update:-</strong></p>
  
  <p>If strategy for MySQL or Oracle is different then please consider oracle as DB</p>