title: Double Dot table qualifier
body: <p>I am looking at a new database schema developed by an external vendor.  There are two databases:</p>
  
  <pre><code>Database1
  Database2
  </code></pre>
  
  <p>They have sent me an SQL statement that joins tables between the two databases.  There are places where they have used a double dot notation.  I have never seen this before.  Please see the SQL statement below (this is not the statement they sent me):</p>
  
  <pre><code>select * from database2..Person
  </code></pre>
  
  <p>The statement above is run from database1.  Why does it have two dots? If I remove one of the dots then the query does not run.</p>
  
  <p>I have done some Googling and came across this: <a href="http://www.sqlservercentral.com/Forums/Topic585446-338-1.aspx" rel="noreferrer">http://www.sqlservercentral.com/Forums/Topic585446-338-1.aspx</a>.  This suggests it is referring to the schema.  However:</p>
  
  <ol>
  <li>The schema is empty in the sql statement i.e. there is no text in between the two dots.</li>
  <li>The Person table is part of the dbo schema in database2.</li>
  </ol>