[cinq]

You should have a form to submit the search keywords, yes ?
Upon submitting of that form, the search keywords would be taken to the script for processing.

In the script,
[sql]
SELECT keywords from resources WHERE keywords LIKE '%$searchword%'
[/sql]
such a query would search for similar items in the db as your 'searchword', which is what you are trying to search.

Then do a check if there are any result rows returned.
If there aren't any results, ( like the e.g you described ), then present an error msg.