title: Oracle index containing all columns of another index, right or wrong
body: <p>I am working on an <code>Oracle 12c</code> database.
  I have a table being queried a lot. One query uses columns A and B in where clause, another query uses A,B,C,D &amp; E columns in the where clause. I want to speed up queries.  </p>
  
  <p>I have added 2 non-unique indexes, one on <strong>A &amp; B</strong> and one on <strong>A &amp; B &amp; C &amp; D &amp; E</strong>, so my second index actually includes the first index columns. Is this right? Technically wrong? Or it depends?</p>
  
  <p>In such cases, in which a table is queried on different columns, what is the best practice for indexes? What are the impacts of indexes?</p>