The database size of a Magento installation, in particular once they have gone live, tends to grow rapidly because Magento keeps track of visitors who visit the site and the url of pages that they visit.
To give you an idea, for a relatively low traffic Magento Site version 220.127.116.11 of ~30 visitors per day and ~10 page clicks per visitor, the database grows at a pace of ~10MB per day.
To reduce the database size, use phpMyAdmin to browse the tables and locate “log_url”, “log_url_info”, “log_visitor”, “log_visitor_info”.
phpMyAdmin tells you in a glance the number of records in these tables and their sizes.
Select these tables and empty them. Confirm to truncate.
In this particular example, I have just reduced the size from ~495MB to ~134MB.