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
What is the sum of total pounds of purchase in year 2018 for all branches in London?
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 as t1 join branch as t2 on t1 . branch_id = t2 . branch_id where t2 . city = value and t1 . year = value
What is the sum of total pounds of purchase in year 2018 for all branches in London ?