I've been getting the following error recently:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '%d ORDER BY created_on ASC LIMIT 4729'
This is caused by the following query, which doesn't replace the %d token:
SELECT * FROM wp_wsal_occurrences WHERE created_on < %d ORDER BY created_on ASC LIMIT 4729