title: Horizontally 'collapse' two columns with matching substrings into one
body: <p>My query results in a table that looks like this:</p>
  
  <pre><code>Unit25  Unit26  Seconds25  Seconds26
  A2501   null     383042     null
  A2502   A2602    354554     35147
  A2503   A2603    344021     33388
  A2504   null     359453     null
  A2505   null     16702      null
  A2507   null     14784      null
  null    A2608    null       16997
  A2509   A2609    13092      358893
  null    A2610    null       291256
  A2511   A2611    18770      369082
  A2512   A2612    8647       null
  A2513   null     65214      null
  </code></pre>
  
  <p>A25s are matched to corresponding A26s by a substring of their last two digits. 
  However, I would like to combine those A25 and A26 columns into something like this:</p>
  
  <pre><code>Unit    TotalSeconds
  01       383042
  02       389701
  03       377409
  04       359453
  05       16702
  07       14784
  08       16997
  09       371985
  10       291256
  11       387852
  12       8647
  13       65214
  </code></pre>
  
  <p>I can get TotalSeconds by using ISNULL to turn those nulls into 0s and adding Seconds25 and Seconds26 together, but I'm not so sure how to turn Unit25 and Unit26 into one column of substrings. Any advice?</p>