Update old database with SQL dump
import your dump with INSERT IGNORE OPTION (skip duplicates)

on your dump file (assuming you're using linux OS)

cat /path/dir/to/dumpfile.sql |
  sed s/"^INSERT"/"INSERT IGNORE"/g &gt; /path/dir/to/newdump.sql


then issue import

mysql -u username -p databasename &lt; /path/dir/to/newdump.sql