title: Combine two integers to create a unique number
body: <p>Good Morning,</p>
  
  <p>I was looking for a way to combine two integers to create a unique number, I have two tables that I need to combine into a third table with unique numbers, </p>
  
  <p>These are my tables:</p>
  
  <pre><code>Table A 
  SchoolID    ClassId
  107 56644231
  107 56644532
  107 320110212
  
  Table B 
  SchoolID    ClassId
  108 566442310
  108 56644532
  108 50110212
  </code></pre>
  
  <p>I need to export these fields to a third table combining class ID and school ID into one single field called classID. I need to be able to combine these numbers together and then be able to uncombine them to get schoolid and classid separate for update purposes. I was thinking of concatenating the strings <code>'schoolid + '00' + 'classid'</code> since I know that schoolid will always be a 3 digit number but I am looking for some other way perhaps mathematical where I don't have to use string casts.</p>
  
  <p>Is there a mathematical way to do this? Or is casting to string the best way to do this?</p>
  
  <p>I am using C# to code the solution.</p>
  
  <p>Thanks,</p>