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Formatted question description: https://leetcode.ca/all/1179.html
1179. Reformat Department Table
Level
Easy
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.
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 |
+------+-------------+-------------+-------------+-----+-------------+
Solution
To split the column revenue according to difference months, use case when. Then use sum to calculate the revenues for each month.
# Write your MySQL query statement below
select id,
sum(case `month` when 'Jan' then revenue end) as Jan_Revenue,
sum(case `month` when 'Feb' then revenue end) as Feb_Revenue,
sum(case `month` when 'Mar' then revenue end) as Mar_Revenue,
sum(case `month` when 'Apr' then revenue end) as Apr_Revenue,
sum(case `month` when 'May' then revenue end) as May_Revenue,
sum(case `month` when 'Jun' then revenue end) as Jun_Revenue,
sum(case `month` when 'Jul' then revenue end) as Jul_Revenue,
sum(case `month` when 'Aug' then revenue end) as Aug_Revenue,
sum(case `month` when 'Sep' then revenue end) as Sep_Revenue,
sum(case `month` when 'Oct' then revenue end) as Oct_Revenue,
sum(case `month` when 'Nov' then revenue end) as Nov_Revenue,
sum(case `month` when 'Dec' then revenue end) as Dec_Revenue
from Department group by id;