title: mysql find records in a table that reference records that don't exist
body: <p>In mysql, if I have a record that references the id of another record.  For example</p>
  
  <pre><code>Table 1
  id          bigint
  tabe2ref    bigint
  
  Table 2
  id          bigint
  </code></pre>
  
  <p>Where table2ref simply references Table2.id.<br>
  Is there a way to list all records in table 1 that reference a record in table 2 where that record doesn't exist?</p>