title: sqldf--select nested in another select doesn't work
body: <p>I'm working with the sqldf package in R. I want to create a dataset whose students' ID are excluded from another dataset. My code looks like:</p>
  
  <pre><code>delete &lt;- sqldf("select distinct ID from A where ...") 
  B&lt;-sqldf("select * from A where ID not in ('select ID from delete')")
  </code></pre>
  
  <p>After running the code I found B is exactly the same as A. It seems sqldf doesn't recogonize the nested select statement.
  Any suggestions would be appreciated!</p>