SQL利用CASE按分组显示合计

按行显示的合计

select
    game,
    sum(purchase) as purchase_sum
from
    purchase
group by
    game;

按列显示的合计

select
    sum(case when game = 'action'
             then purchase else 0 end) as sum_action,
    sum(case when game = 'puzzle'
             then purchase else 0 end) as sum_puzzle,
    sum(case when game = 'RPG'
             then purchase else 0 end) as sum_rpg
from
    purchase;