title: How to add indexes to the following examples？
body: <pre><code>SELECT UNIT_PRICE
  FROM ORDER_DETAIL
  WHERE QUANTITY IN (100, 200, 300) OR
  DISCOUNT = 0.01;
  </code></pre>
  <p>My query:</p>
  <pre><code>EXPLAIN PLAN FOR SELECT UNIT_PRICE FROM ORDER_DETAIL WHERE QUANTITY IN (100, 200, 300) OR DISCOUNT = 0.01;`
  SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);
  CREATE INDEX OD_IDX_QD ON ORDER_DETAIL(QUANTITY, DISCOUNT);
  EXPLAIN PLAN FOR SELECT UNIT_PRICE FROM ORDER_DETAIL WHERE QUANTITY IN (100, 200, 300) OR DISCOUNT = 0.01;
  SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);
  DROP INDEX OD_IDX_QD;
  </code></pre>
  <p><a href="https://i.stack.imgur.com/zYBw7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zYBw7.png" alt="Before adding index" /></a></p>
  <p><a href="https://i.stack.imgur.com/U1J70.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/U1J70.png" alt="After adding index" /></a></p>
  <p>How to add index correctly in this case？</p>