title: sub query or join?
body: <p>I am wondering if anyone can explain to me when you would use a sub query and when you would use a join.</p>
  
  <p>for example.</p>
  
  <p>I have this query:</p>
  
  <p><code>SELECT * from contacts where id in (select contactId from contactgrouplink where groupId = 1);</code></p>
  
  <p>What would the benefit be of a join over this sub query?</p>