Reformat Department Table

Author: ignacio-chiazzo

LeetcodeProblems/Databases/Reformat_Department_Table.sql

@@ -0,0 +1,131 @@
+/*
+Reformat Department Table
+https://leetcode.com/problems/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.
+
+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).
+*/
+
+
+
+
+-- better solution
+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
+
+
+-- bad solution
+with jan AS (
+    SELECT id, revenue AS Jan_Revenue
+    FROM Department
+    WHERE month = "Jan"
+), feb AS (
+    SELECT id, revenue AS Feb_Revenue
+    FROM Department
+    WHERE month = "Feb"
+), mar AS (
+    SELECT id, revenue AS Mar_Revenue
+    FROM Department
+    WHERE month = "Mar"
+), apr AS (
+    SELECT id, revenue AS Apr_Revenue
+    FROM Department
+    WHERE month = "Apr"
+), may AS (
+    SELECT id, revenue AS May_Revenue
+    FROM Department
+    WHERE month = "May"
+), jun AS (
+    SELECT id, revenue AS Jun_Revenue
+    FROM Department
+    WHERE month = "Jun"
+), jul AS (
+    SELECT id, revenue AS Jul_Revenue
+    FROM Department
+    WHERE month = "Jul"
+), aug AS (
+    SELECT id, revenue AS Aug_Revenue
+    FROM Department
+    WHERE month = "Aug"
+), sep AS (
+    SELECT id, revenue AS Sep_Revenue
+    FROM Department
+    WHERE month = "Sep"
+), oct AS (
+    SELECT id, revenue AS Oct_Revenue
+    FROM Department
+    WHERE month = "Oct"
+), nov AS (
+    SELECT id, revenue AS Nov_Revenue
+    FROM Department
+    WHERE month = "Nov"
+), decemb AS (
+    SELECT id, revenue AS Dec_Revenue
+    FROM Department
+    WHERE month = "Dec"
+)
+    
+SELECT Distinct(Department.id),  jan.Jan_Revenue,  feb.Feb_Revenue,  mar.Mar_Revenue,  apr.Apr_Revenue,  may.May_Revenue,   jun.Jun_Revenue,  jul.Jul_Revenue,  aug.Aug_Revenue,  sep.Sep_Revenue, oct.Oct_Revenue, nov.Nov_Revenue,  decemb.Dec_Revenue
+    FROM Department LEFT JOIN jan using(id)
+    LEFT JOIN feb using(id) 
+    LEFT JOIN mar using(id)
+    LEFT JOIN apr using(id)
+    LEFT JOIN may using(id)
+    LEFT JOIN jun using(id)
+    LEFT JOIN jul using(id)
+    LEFT JOIN aug using(id)
+    LEFT JOIN sep using(id)
+    LEFT JOIN oct using(id)
+    LEFT JOIN nov using(id)
+    LEFT JOIN decemb using(id)
+    

README.md

@@ -88,6 +88,7 @@ To run a specific problem in your console, go to the file test, add the call to
 | [Combine Two Tables](/LeetcodeProblems/Databases/Combine_Two_Tables.sql) | Easy   | https://leetcode.com/problems/combine-two-tables |
 | [Second Highest Salary](/LeetcodeProblems/Databases/Second_highest_salary.sql)| Easy   | https://leetcode.com/problems/second-highest-salary |
 | [Customers Who Never Order](/LeetcodeProblems/Databases/Customers_Who_Never_Order.sql)| Easy |  https://leetcode.com/problems/customers-who-never-order |
+| [Reformat Department Table](/LeetcodeProblems/Databases/Reformat_Department_Table.sql) | Easy | https://leetcode.com/problems/reformat-department-table |
 
 ### UtilsClasses