title: Indexes in Oracle
body: <p>As always, I apologize if this is a stupid question (two questions, actually). I'm not a DBA, so I know very little about indexes. My questions are:</p>
  
  <ol>
  <li><p>Is there any cutoff point (in terms of number of rows) at which an index would be pointless? For example, is there any benefit to an index on a lookup table with 10-20 rows?</p></li>
  <li><p>I've read some things about covering indexes in Oracle, and the concept makes sense in that the data can be retrieved directly from the index and a trip to the table is unnecessary. How can I tell if an index is a covering index? Is this a value set when the index is created, or by default based on the rows that the index includes?</p></li>
  </ol>
  
  <p>I hope this makes sense.</p>