title: Comparing two table columns to see what one table is missing
body: <p>So currently I have two tables, </p>
  
  <pre><code>Servers              Admins
  -------             --------
  ServerID             AdminID
  ServerName           AdminFirstName
  Server location      AdminFirstName 
  AdminID
  </code></pre>
  
  <p>What I am currently trying to do is go through the <code>AdminID</code> column in the <code>Servers</code> table and compare it to the <code>AdminID</code> column in the <code>Admins</code> table.
  The comparison I'm trying to make is "What admins have not been assigned to a server yet?", and "What servers do not have an admin assigned to them yet?"</p>
  
  <p>I have tried the following (to attempt the first question):</p>
  
  <pre><code>SELECT CONCAT(AdminLastName,',',AdminFirstName)
  FROM Admins
  WHERE AdminID NOT IN(SELECT AdminID FROM Servers)
  </code></pre>
  
  <p>The query is returning 0 results, when it should be returning a few.
  Since both questions can be answered with virtually the same logic, I just need a push in the right direction as to why this is not working. </p>
  
  <p>Thanks in advance</p>