ในปี 2018 มีการซื้อสาขาในลอนดอนทั้งหมดจำนวนเท่าใดในปี 2018?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
How many total pounds were purchased in the year 2018 at all London branches?It is not neccessary to use all the tables.
 purchase:  member_id [ number]  branch_id [ text]  year [ text]  total_pounds [ number] 
SELECT SUM(total_pounds) FROM purchase AS T1 JOIN branch AS T2 ON T1.branch_id = T2.branch_id WHERE T2.city = 'London' AND T1.year = 2018