This snippet will select Webform (Webform module) submitted data between a given date range. In this case, that date range is between 2009-06-04 and 2009-07-07.
The UNIX_TIMESTAMP function converts the date into a Unix Timestamp. This is because the value of submitted is in Unix Timestamp format.
SELECT sub.sid, data.data, FROM_UNIXTIME(submitted, '%d/%m/%Y') FROM webform_submissions as sub, webform_submitted_data as data WHERE sub.sid = data.sid AND submitted >= UNIX_TIMESTAMP('2009-06-04 00:00:01') AND submitted <= UNIX_TIMESTAMP('2009-07-07 23:59:59');