Incorrect DATETIME value: ''<br />select discount_percentage, discount_start_date, discount_expire_date
		from tbl_category, tbl_category_item_map
		where tbl_category.category_id = tbl_category_item_map.category_id
		and (discount_start_date <= now() or discount_start_date is NULL or discount_start_date = '')
		and (discount_expire_date > now() or discount_expire_date is NULL or discount_expire_date = '')
		and item_id = 721
		order by discount_percentage DESC
		limit 0,1