title: SQL/ACCESS one-sided one-to-one relationship data integrity
body: <p>I have a DB that contains two tables for now:</p>
  <ul>
  <li><strong>&quot;Users&quot;:</strong> includes data loaded from a CSV.</li>
  <li><strong>&quot;Accounts&quot;:</strong> Account opened for a certain user.</li>
  </ul>
  <p>Both tables have numeric ID field (&quot;UserID&quot;, &quot;AccountID&quot;), as the &quot;Accounts&quot; table also has a field called &quot;UserID&quot; for linking these two tables together.</p>
  <p>I wish to connect these two tables to make sure that new records in &quot;Accounts&quot; can be added only if they have a matching inserted UserID that is found in the &quot;Users&quot; table. It sounded to me at first like a connection of one-to-one. However, while there can't be an account with a user that is not in the &quot;Users&quot; table, most of the records in &quot;Users&quot; still don't have an account in the &quot;Accounts&quot; table.</p>
  <p>Is there any way to enforce data integrity about this relationship in ACCESS/SQL?</p>