CREATE TABLE purchase (member_id NUMBER, branch_id CLOB, year CLOB, total_pounds NUMBER)
CREATE TABLE membership_register_branch (member_id NUMBER, branch_id CLOB, register_year CLOB)
CREATE TABLE branch (branch_id NUMBER, name CLOB, open_year CLOB, address_road CLOB, city CLOB, membership_amount CLOB)
CREATE TABLE member (member_id NUMBER, card_number CLOB, name CLOB, hometown CLOB, level NUMBER)

How many total pounds were purchased in the year 2018 at all London branches?
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
SELECT SUM("total_pounds") FROM "purchase" "T1" JOIN "branch" "T2" ON "T1"."branch_id" = "T2"."branch_id" AND "T2"."city" = 'London' WHERE "T1"."year" = 2018