Timely and auto send email

User requesting to be made aware of:

[henry0]

Project:
A registered user may enter in its reserved area a few key words that will be entered in the DB and used for a query.
If keywords found then sending an auto-email
So far so good
But main question is:
How can I set a system that will on its own timely query the DB for example every 3 hours

[willybfriendly]

This would require a chron job. You can Google chron tab, chron job, etc. for techniques and specifics.

WBF