title: unique indexes and include statements
body: <h2>create unique index</h2>
  
  <p>In DB2 UDB I can create an index using the following syntax  </p>
  
  <pre><code>create unique index I_0004 on TABLENAME (a) INCLUDE (b, c, d);
  </code></pre>
  
  <p>where a, b, c and d are field of the table <code>TABLENAME</code>.  </p>
  
  <p>In DB2 for os390 this syntax (the <code>INCLUDE</code> keyword) is not allowed, so I am creating     the indexes as follows  </p>
  
  <pre><code>create unique index I_0004 on TABLENAME (a);  
  create index I_0005 on TABLENAME (a, b, c, d);
  </code></pre>
  
  <p>Are the two statements above equivalent to the solution with the <code>INCLUDE</code> keyword?  </p>
  
  <h2>index columns order</h2>
  
  <p>And, if I slightly modify the first statement</p>
  
  <pre><code>create index I_0005 on TABLENAME (a, b, c, d) ALLOW REVERSE SCANS;  
  </code></pre>
  
  <p>is this <code>ALLOW REVERSE SCANS</code> equivalent to creating indexes</p>
  
  <pre><code>create index I_0005 on TABLENAME (a, b, c, d);  
  create index I_0005 on TABLENAME (d, c, b, a);  
  </code></pre>
  
  <p>or does it consider also any combination of the given columns (I mean, a,b,c,d; b,c,d,a; c,d,a,b; and so on...)?</p>