1179. 重新格式化部门表 SQL架构 部门表 Department： +---------------+---------+ | Column Name | Type | +---------------+---------+ | id | int | | revenue | int | | month | varchar | +---------------+---------+ (id, month) 是表的联合主键。 这个表格有关于每个部门每月收入的信息。 月份（month）可以取下列值 ["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"]。 编写一个 SQL 查询来重新格式化表，使得新的表中有一个部门 id 列和一些对应 每个月 的收入（revenue）列。 查询结果格式如下面的示例所示： Department 表： +------+---------+-------+ | id | revenue | month | +------+---------+-------+ | 1 | 8000 | Jan | | 2 | 9000 | Jan | | 3 | 10000 | Feb | | 1 | 7000 | Feb | | 1 | 6000 | Mar | +------+---------+-------+ 查询得到的结果表： +------+-------------+-------------+-------------+-----+-------------+ | id | Jan_Revenue | Feb_Revenue | Mar_Revenue | ... | Dec_Revenue | +------+-------------+-------------+-------------+-----+-------------+ | 1 | 8000 | 7000 | 6000 | ... | null | | 2 | 9000 | null | null | ... | null | | 3 | null | 10000 | null | ... | null | +------+-------------+-------------+-------------+-----+-------------+ 注意，结果表有 13 列 (1个部门 id 列 + 12个月份的收入列)。
# Write your MySQL query statement below select id , sum(case `month` when 'Jan' then revenue else null end) as Jan_Revenue , sum(case `month` when 'Feb' then revenue else null end) as Feb_Revenue , sum(case `month` when 'Mar' then revenue else null end) as Mar_Revenue , sum(case `month` when 'Apr' then revenue else null end) as Apr_Revenue , sum(case `month` when 'May' then revenue else null end) as May_Revenue , sum(case `month` when 'Jun' then revenue else null end) as Jun_Revenue , sum(case `month` when 'Jul' then revenue else null end) as Jul_Revenue , sum(case `month` when 'Aug' then revenue else null end) as Aug_Revenue , sum(case `month` when 'Sep' then revenue else null end) as Sep_Revenue , sum(case `month` when 'Oct' then revenue else null end) as Oct_Revenue , sum(case `month` when 'Nov' then revenue else null end) as Nov_Revenue , sum(case `month` when 'Dec' then revenue else null end) as Dec_Revenue from Department group by id