title: MySQL find missing numbers in (unique) NON-SEQUENTIAL integer field
body: <p>I have a column of non-sequential unique integer numbers between 30 and 999.</p>
  <p>I need to present a dropdown list populated with the available numbers.</p>
  <p>I could use some of the solutions on this forum but they are all meant for sequential number fields.</p>
  <p>I could also probably process this using code in my app, but that is much slower.
  I believe in letting the database engine do as much of the work as possible.</p>
  <p>Is there a way to sort a table field (i.e. create a sequential list) before processing it?</p>