title: Join two datasets based on an inequality condition
body: <p>I have used the call below to "join" my datasets based on an inequality condition: </p>
  
  <pre><code>library(sqldf)
  
  sqldf("select *
  from dataset1 a,
  dataset2 b
  a.col1 &lt;= b.col2")
  </code></pre>
  
  <p>However, is there a way I can do this without <strong>sqldf</strong>?</p>
  
  <p>So far, I can only see merge functions that are based on simple joins on a particular common column.</p>
  
  <p>Thanks!</p>