title: oracle index for string column - does format of data affects quality of index?
body: <p>We have following type of "Unique ID" column for many tables in the database (Oracle). It is a string with following format</p>
  
  <pre><code>&lt;randomnumber&gt;-&lt;ascendingnumber&gt;-&lt;machinename&gt;
  </code></pre>
  
  <p>So we have some thing like this</p>
  
  <pre><code>U1234-12345-NBBJD
  U1234-12346-NBBJD
  U1234-12347-NBBJD
  U1234-12348-NBBJD
  U1234-12349-NBBJD
  </code></pre>
  
  <p>The UID value is unique, we have unique index on them.   Does the following format is more efficient than above for index scans?</p>
  
  <pre><code>NBBJD-U1234-12345
  NBBJD-U1234-12346
  NBBJD-U1234-12347
  NBBJD-U1234-12348
  NBBJD-U1234-12349
  </code></pre>