query to find information that ISNT there?

[ejwf]

Hello
This might be a strange way of going about things but I have a database that holds data updated by users via a website.
I want to be able to see who hasn't up-dated their information that month and send them an e-mail to remind them saying the following records need updating please do it now and then list the records that need to be updated (am I making any sense?)

Example:

I have a table of items that need information , the records are listed as
Item1
Item2
Item3 etc. etc.

then another table that has the updated records
blue
red
blue
red
red
yellow
blue etc.etc.

then another table that keeps tabs on when the records should be submitted by
logFeb
logMar
logApr etc.etc.

So I can query the database and find that 'Item1' has a record for 'LogMar' which is 'red'

But how do I turn this around and say it is now the end of March which items do not have a record entered ?

Hope you can understand what I am trying to do here
TIA

[liquorvicar]

have you investigated MySQL's Timestamp column type?
http://dev.mysql.com/doc/mysql/en/datetime.html