This morning I needed to add a single record to an existing table in database1 from an existing table in database2. Here’s how I was able to do it:
INSERT INTO database1.dbo.tablename SELECT * FROM database2.dbo.tablename WHERE ID='4d08aeb0bedd01452dfef3eabc2816dcc75533c8'
Please note that the databases use a SHA-1 Hash for the ID field. If you use an IDENTITY field in SQL you’d have to take some extra steps to briefly allow inserting an IDENTITY field.