how to test DB if it has been updated?

[greggustin 0]

small MySQL DB => only three rows (ID, GroupID, title, MSG, etc)
The Group ID is unique
I have a php file that prints a table based on the fields
this php file checks on a time schedule to see if the ID has changed
(no change - no display // new ID = new display)
easy when I made a NEW post (Insert) to table (ie ID was auto-increment)

what "trick" can I do when doing Update? without making the user place a NEW value somewhere?

[AndyB 0]

At time1, get the highest id value ( ORDER by id DESC limit 1) and write it to a text file.

At time2, get the highest id value and compare it with the value in the text file. If they match, then no display. If they don't then display AND write a new 'highest' value to the text file.