title: Can I do a `select * from tbl where id in (<string from another query>)
body: <p>Say I want to perform the following query in mysql:</p>
  
  <pre><code>select id from tbl where id in (2,3)
  </code></pre>
  
  <p>but the string '2,3' is already stored in another table's column, say <code>tbl2.data</code>. Is it possible to do something similar to the following:</p>
  
  <pre><code>select id from tbl where id in (select data from tbl2 where x=y);
  </code></pre>
  
  <p>When I tried it, the result was equal to </p>
  
  <pre><code>select id from tbl where id in (2);
  </code></pre>
  
  <p>as if the result was converted to the first number</p>