表 Department：
+---------------+---------+ | Column Name | Type | +---------------+---------+ | id | int | | revenue | int | | month | varchar | +---------------+---------+ 在 SQL 中，(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"]。
重新格式化表格，使得 每个月 都有一个部门 id 列和一个收入列。
以 任意顺序 返回结果表。
结果格式如以下示例所示。
示例 1：
输入： Department table: +------+---------+-------+ | id | revenue | month | +------+---------+-------+ | 1 | 8000 | Jan | | 2 | 9000 | Jan | | 3 | 10000 | Feb | | 1 | 7000 | Feb | | 1 | 6000 | Mar | +------+---------+-------+ 输出： +------+-------------+-------------+-------------+-----+-------------+ | id | Jan_Revenue | Feb_Revenue | Mar_Revenue | ... | Dec_Revenue | +------+-------------+-------------+-------------+-----+-------------+ | 1 | 8000 | 7000 | 6000 | ... | null | | 2 | 9000 | null | null | ... | null | | 3 | null | 10000 | null | ... | null | +------+-------------+-------------+-------------+-----+-------------+ 解释：四月到十二月的收入为空。 请注意，结果表共有 13 列（1 列用于部门 ID，其余 12 列用于各个月份）。
SELECT id,
SUM(CASE WHEN month='Jan' THEN revenue END) AS Jan_Revenue,
SUM(CASE WHEN month='Feb' THEN revenue END) AS Feb_Revenue,
SUM(CASE WHEN month='Mar' THEN revenue END) AS Mar_Revenue,
SUM(CASE WHEN month='Apr' THEN revenue END) AS Apr_Revenue,
SUM(CASE WHEN month='May' THEN revenue END) AS May_Revenue,
SUM(CASE WHEN month='Jun' THEN revenue END) AS Jun_Revenue,
SUM(CASE WHEN month='Jul' THEN revenue END) AS Jul_Revenue,
SUM(CASE WHEN month='Aug' THEN revenue END) AS Aug_Revenue,
SUM(CASE WHEN month='Sep' THEN revenue END) AS Sep_Revenue,
SUM(CASE WHEN month='Oct' THEN revenue END) AS Oct_Revenue,
SUM(CASE WHEN month='Nov' THEN revenue END) AS Nov_Revenue,
SUM(CASE WHEN month='Dec' THEN revenue END) AS Dec_Revenue
FROM department
GROUP BY id