title: Is there a way to set the value of #define on runtime?
body: <p>I wonder if there is a way to set the value of #define in run time.</p>
  
  <p>I assume that there is a query for Oracle specific and Sql Server specific at the code below.</p>
  
  <pre><code>#define oracle
  
  // ...    
  
  #if oracle
  // some code
  #else
  // some different code.
  #endif
  </code></pre>