SELECT * INTO CustomersTOnextDB IN 'BackupDB'
SELECT * INTO BackupDB..CustomersTOnextDB FROM Customers;
or ... if the CustomersTOnextDB table already exists, in the BackupDB database, then
INSERT INTO BackupDB..CustomersTOnextDB SELECT * FROM Customers;
This assumes that the columns in BackupDB..CustomersTOnextDB table are in the same sequence as the column in the Customers table in the connected-database. This is a somewhat risky proposition as that may change in the future. SELECT * is always risky in that regard, so you might prefer to do
INSERT INTO BackupDB..CustomersTOnextDB ( Col1, Col2, ... ) SELECT Col1, Col2, ... FROM Customers;