clear a mysql table

I need to clear a table (cache) from a database based on the database size. Our web site uses cached pages. Our webhost only allow us 100 MB storage. Usually the database is just 10 MB, but when a search engine crawls our calendar, then the storage is quickly 108 MB. The system reports then mathematically correct: Space left on database -8MB !!! I plan therefore a web page, which is triggered by cron every hour and will just clear the table. Can I use just: mysql_query("DELETE FROM cash") or die(mysql_error()); or do I need to loop through all records? or is there a better solution? How can I get the database size? bye R.