Make a database dump just before you make a change
Dump as a sql file - phpmyadmin->export or pgadmin3->backup (select 'insert commands' in the options will be easier to read)
Do what you need to do then repeat the above.
Name the dumps as beforeaction.sql and afteraction.sql
Then from a terminal enter
diff -u -s beforeaction.sql afteraction.sql > changes.txt
Open changes.txt in your favourite editor.
Any line beginning with a +INSERT will be a new record.
Any lines beginning with -INSERT will have a matching +INSERT and will be an UPDATE - just look for the differences in the columns.
Thats it :)