Update Tables Of 2 muliple databases in bulk

 UPDATE db1.dbo.tblA
SET Coulmnname = db2.DBO.tblA.Coulmnname
FROM db2.DBO.tblA INNER JOIN db1.dbo.tblA ON
db2.DBO.tblA.PKCOULMN = db1.dbo.tblA.PKCOULMN