1179 Reformat Department Table 重新格式化部门表
Description:
Table: Department
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| revenue | int |
| month | varchar |
+---------------+---------+
(id, month) is the primary key of this table.
The table has information about the revenue of each department per month.
The month has values in ["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"].
Write an SQL query to reformat the table such that there is a department id column and a revenue column for each month.
Example:
The query result format is in the following example:
Department table:
+------+---------+-------+
| id | revenue | month |
+------+---------+-------+
| 1 | 8000 | Jan |
| 2 | 9000 | Jan |
| 3 | 10000 | Feb |
| 1 | 7000 | Feb |
| 1 | 6000 | Mar |
+------+---------+-------+
Result table:
+------+-------------+-------------+-------------+-----+-------------+
| id | Jan_Revenue | Feb_Revenue | Mar_Revenue | ... | Dec_Revenue |
+------+-------------+-------------+-------------+-----+-------------+
| 1 | 8000 | 7000 | 6000 | ... | null |
| 2 | 9000 | null | null | ... | null |
| 3 | null | 10000 | null | ... | null |
+------+-------------+-------------+-------------+-----+-------------+
Note that the result table has 13 columns (1 for the department id + 12 for the months).
题目描述:
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。
示例 :
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)。
思路:
行转列
代码:
MySQL:
# Write your MySQL query statement below
SELECT
id,
MAX(IF(month = 'Jan', revenue, null)) AS "Jan_Revenue",
MAX(IF(month = 'Feb', revenue, null)) AS "Feb_Revenue",
MAX(IF(month = 'Mar', revenue, null)) AS "Mar_Revenue",
MAX(IF(month = 'Apr', revenue, null)) AS "Apr_Revenue",
MAX(IF(month = 'May', revenue, null)) AS "May_Revenue",
MAX(IF(month = 'Jun', revenue, null)) AS "Jun_Revenue",
MAX(IF(month = 'Jul', revenue, null)) AS "Jul_Revenue",
MAX(IF(month = 'Aug', revenue, null)) AS "Aug_Revenue",
MAX(IF(month = 'Sep', revenue, null)) AS "Sep_Revenue",
MAX(IF(month = 'Oct', revenue, null)) AS "Oct_Revenue",
MAX(IF(month = 'Nov', revenue, null)) AS "Nov_Revenue",
MAX(IF(month = 'Dec', revenue, null)) AS "Dec_Revenue"
FROM
Department
GROUP BY id;