Merge two SQL tables without duplicate

INSERT INTO BBB(id, timestamp, mycount, col1, col2, col3, etc.)
SELECT id, timestamp, mycount, col1, col2, col3, etc.
   FROM AAA
   WHERE
       NOT EXISTS(SELECT NULL FROM BBB oldb WHERE
          oldb.col1 = AAA.col1
          AND oldb.col2 = AAA.col2
          AND oldb.col3 = AAA.col3

       )

Add columns as needed to the NOT EXISTS clause.

Source: http://stackoverflow.com/questions/9747337/merging-content-of-two-tables-without-duplicating-content