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;