ราคาของ oxybutynin คืออะไร?ไม่จำเป็นต้องใช้ตารางทั้งหมด
what is the price for the oxybutynin?It is not neccessary to use all the tables.
 d_items:  row_id [ number]  itemid [ number]  label [ text]  linksto [ text] 
SELECT DISTINCT cost.cost FROM cost WHERE cost.event_type = 'prescriptions' AND cost.event_id IN (SELECT prescriptions.row_id FROM prescriptions WHERE prescriptions.drug = 'oxybutynin')