When several connections are established in Database Explorer, you can execute queries or perform another actions with either of them. SQL documents are associated with a connection which you can set on the Connection toolbar. The drop-down list box on the toolbar shows what connection is associated with an active document or tool window.
When creating or opening a SQL document, it is assigned to a default connection. If you create a SQL document with no connection present in Database Explorer, the document will have no connection and you can not execute SQL or retrieve data. You can change connection for SQL document by selecting required connection from the Document Connection drop-down list box on the Connection toolbar.