[1179] Reformat Department Table

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.

Return the result table in any order.

The query result format is in the following example.

 

Example 1:

Input: 
Department table:
+------+---------+-------+
| id   | revenue | month |
+------+---------+-------+
| 1    | 8000    | Jan   |
| 2    | 9000    | Jan   |
| 3    | 10000   | Feb   |
| 1    | 7000    | Feb   |
| 1    | 6000    | Mar   |
+------+---------+-------+
Output: 
+------+-------------+-------------+-------------+-----+-------------+
| id   | Jan_Revenue | Feb_Revenue | Mar_Revenue | ... | Dec_Revenue |
+------+-------------+-------------+-------------+-----+-------------+
| 1    | 8000        | 7000        | 6000        | ... | null        |
| 2    | 9000        | null        | null        | ... | null        |
| 3    | null        | 10000       | null        | ... | null        |
+------+-------------+-------------+-------------+-----+-------------+
Explanation: The revenue from Apr to Dec is null.
Note that the result table has 13 columns (1 for the department id + 12 for the months).

 

문제 조건 

• 각 월에 대한 부서 ID와 수익을 출력하시오. 

# pivot, case when... 
SELECT  id, 
        SUM(CASE WHEN month = "Jan" THEN revenue ELSE NULL END) AS Jan_Revenue,
        SUM(CASE WHEN month = "Feb" THEN revenue ELSE NULL END) AS Feb_Revenue,
        SUM(CASE WHEN month = "Mar" THEN revenue ELSE NULL END) AS Mar_Revenue,
        SUM(CASE WHEN month = "Apr" THEN revenue ELSE NULL END) AS Apr_Revenue,
        SUM(CASE WHEN month = "May" THEN revenue ELSE NULL END) AS May_Revenue,
        SUM(CASE WHEN month = "Jun" THEN revenue ELSE NULL END) AS Jun_Revenue,
        SUM(CASE WHEN month = "Jul" THEN revenue ELSE NULL END) AS Jul_Revenue,
        SUM(CASE WHEN month = "Aug" THEN revenue ELSE NULL END) AS Aug_Revenue,
        SUM(CASE WHEN month = "Sep" THEN revenue ELSE NULL END) AS Sep_Revenue,
        SUM(CASE WHEN month = "Oct" THEN revenue ELSE NULL END) AS Oct_Revenue,
        SUM(CASE WHEN month = "Nov" THEN revenue ELSE NULL END) AS Nov_Revenue,
        SUM(CASE WHEN month = "Dec" THEN revenue ELSE NULL END) AS Dec_Revenue
FROM department
GROUP BY id