title: mysql operand should contain 1 column(s)
body: <p>My current query is this:</p>
  
  <pre><code>DELETE FROM a WHERE id=1
  </code></pre>
  
  <p>When I try to run it, I get the 1241 error code that the operand should contain 1 column(s).  I have also tried:</p>
  
  <pre><code>DELETE FROM a
  WHERE id = (SELECT id
  FROM (SELECT * FROM a WHERE a=1) AS a2)
  </code></pre>
  
  <p>Which also returns the same error when I run it.  This seems strange to be because I'm fairly certain I'm selecting only 1 column, and the output is only one column when I just run the inner select query.</p>
  
  <p>But when I try:</p>
  
  <pre><code>DELETE FROM b WHERE id=1
  </code></pre>
  
  <p>The correct queries are deleted without issue.  Table <code>a</code> has <code>id</code> as its primary key, while table <code>b</code> has <code>id</code> as a foreign key.</p>
  
  <p>Can anyone shed any light into this?</p>