使用MySql透视数据

Question

Objective 1: Your sales data is stored in the Purchases table. Your sales staff wants to see the sales data in a pivoted form, broken down by quarter.

If your Purchases table doesn't have sales data, create some. Be sure the data spans four quarters. Next, write a query to pivot the data as follows:

Album              Q1   Q2   Q3   Q4

OK Computer        2    5    3    7

 Sea Change        8    6    2    1 

Do not create a separate table or a view. Do not alter any tables.

Save your query as dba1lesson10project1.sql and hand in the project.

This is What I need to do. But, the table it wants me to work with looks like this. And it states in the assignment I cannot alter it at all.

CustomerID    DateOfPurchase   SongID

1              2007-03-31        3
3              2007-06-30        4
4              2007-09-30        4
5              2007-12-31        5

I have tried

  SELECT SongID,
  SUM(CASE WHEN DateOfPurchase = '2007-03-31' THEN DateOfPurchase ElSE 0 END) AS 'Q1',
  SUM(CASE WHEN DateOfPurchase = '2007-06-30' THEN DateOfPurchase ELSE 0 END) AS 'Q2',
  SUM(CASE WHEN DateOfPurchase = '2007-09-30' THEN DateOfPurchase ELSE 0 END) AS 'Q3',
  SUM(CASE WHEN DateOfPurchase = '2007-12-31' THEN DateOfPurchase ELSE 0 END) AS 'Q4'
  FROM Purchases
  GROUP BY SongID;

Along with other variants:

  SELECT SongID,
  SUM(CASE WHEN DateOfPurchase = '2007-03-31' THEN CustomerID ElSE 0 END) AS 'Q1',
  SUM(CASE WHEN DateOfPurchase = '2007-06-30' THEN CustomerID ELSE 0 END) AS 'Q2',
  SUM(CASE WHEN DateOfPurchase = '2007-09-30' THEN CustomerID ELSE 0 END) AS 'Q3',
  SUM(CASE WHEN DateOfPurchase = '2007-12-31' THEN CustomerID ELSE 0 END) AS 'Q4'
  FROM Purchases
  GROUP BY SongID;

And:

  SELECT SongID,
  SUM(CASE WHEN DateOfPurchase = '2007-03-31' THEN SongID ElSE 0 END) AS 'Q1',
  SUM(CASE WHEN DateOfPurchase = '2007-06-30' THEN SongID ELSE 0 END) AS 'Q2',
  SUM(CASE WHEN DateOfPurchase = '2007-09-30' THEN SongID ELSE 0 END) AS 'Q3',
  SUM(CASE WHEN DateOfPurchase = '2007-12-31' THEN SongID ELSE 0 END) AS 'Q4'
  FROM Purchases
  GROUP BY SongID;

Which, the last 2 almost get me what I need. But, there is only one purchase per SongID and Quarter. They show me either the CustomerID or SongID instead. I have a basic understand of what I need to do. But without being able to alter the table to show how many purchases there have actually been I'm not sure what to do. Any suggestions?

Answer 1

Your current query is very close, I would suggest a few minor changes. You are hard-coding the date but what happens if you have a date in quarter one that is not equal to 2007-03-31 it won't show up.

I would use the QUARTER() function in MySQL, this will return the quarter 1-4 based on the date value.

Second, I don't think you want to sum the SongID , in your CASE expression I would replace the SongID with 1 similar to the following:

SELECT SongID,
  SUM(CASE WHEN Quarter(DateOfPurchase) = 1 THEN 1 ElSE 0 END) AS Q1,
  SUM(CASE WHEN Quarter(DateOfPurchase) = 2 THEN 1 ELSE 0 END) AS Q2,
  SUM(CASE WHEN Quarter(DateOfPurchase) = 3 THEN 1 ELSE 0 END) AS Q3,
  SUM(CASE WHEN Quarter(DateOfPurchase) = 4 THEN 1 ELSE 0 END) AS Q4
FROM Purchases
GROUP BY SongID;

See SQL Fiddle with Demo

Answer 2

You can do this quarterly report easily using MySQL Pivot table generator . While creating your report, you will be asked to add the "Column settings " Please choose the "Purchasing table" as the " Table ", the column that contains the date values as the " Field " . Once selecting a date value, a function menu should appear, please select " Quarter " to get your pivot table divided in quarters as you requested. please note that you have the option to create a report for one specific year if you like and in this case you should check the " Exact Year " Box and add a specific year otherwise leave the " Exact year " box unchecked .

The final report will be able to see something like this report :

http://mysqlpivottable.net/MySQL-Pivot-Table-Demo/tables/Quarterly_Sales_Report/