title: Query data from both SQL Server and Azure DocumentDB?
body: <p>We have quite a big SQL server database which keeps track of subscribers to email newsletters (currently about 100k users) and we're building something that will track data for each newsletter sent, including whether each person has bounced/received/viewed/clicked an email. So, this could result in millions of rows in the statistics tables and we were thinking of trying out Document DB for the first time.</p>
  
  <p>My question is whether it's possible to query data in SQL server and Document DB at the same time. Maybe there is a way to join directly, or by using LINQ in c#. I'm no expert but I know that you can query multiple SQL server databases at the same time.</p>
  
  <p>The main thing is that we need to be able to cross-reference the main Subscribers list with all the data kept in Document DB by using their unique subscriber ID.</p>