Aggregation comparison query

Question

I have the following table of offers on iTunes, Google Play, and Microsoft:

`offers`
- id
- Title
- Year
- Platform
- Offer

An example entry might be something like:

(1, 'Titanic', 1997, 'iTunes', 'HDBUY')

This would mean that the film title Titanic (1997) is available for HDBUY on iTunes.

I have multiple platforms and I'd like to compare iTunes to other platforms to see which platform has more offers per title. Ideally, the result of my query would look like the following:

Title        Year        iTunes_Offers        Top_Platform_Offers         Top_Platform
Titanic      1997        HDBUY,SDBUY          HDBUY,SDBUY,SDRENT          Microsoft
Avatar       2009                             HDBUY                       Google

Here is a schema with sample data to test with:

CREATE TABLE `offers` (
  `id` varchar(20) DEFAULT NULL,
  `Title` varchar(100) DEFAULT NULL,
  `Year` varchar(20) DEFAULT NULL,
  `Platform` varchar(100) DEFAULT NULL,
  `Offer` varchar(20) DEFAULT NULL
);

INSERT INTO `offers` (`id`, `Title`, `Year`, `Platform`, `Offer`)
VALUES
    ('1', 'Titanic', '1997', 'iTunes', 'HDBUY'),
    ('1', 'Titanic', '1997', 'iTunes', 'SDBUY'),
    ('2', 'Titanic', '1997', 'Microsoft', 'SDBUY'),
    ('2', 'Titanic', '1997', 'Microsoft', 'HDBUY'),
    ('2', 'Titanic', '1997', 'Microsoft', 'SDRENT'),
    ('3', 'Titanic', '1997', 'Google', 'HDBUY'),
    ('4', 'Avatar', '2009', 'Google', 'HDBUY');

I can get all the offers per platform by doing the following query:

SELECT Title, Year, Platform, GROUP_CONCAT(Offer) GROUP BY id

Which gives me:

id  Title   Year    Platform    Offer   group_concat(offer)
1   Titanic 1997    iTunes  HDBUY   HDBUY,SDBUY
2   Titanic 1997    Microsoft   SDBUY   SDBUY,HDBUY,SDRENT
3   Titanic 1997    Google  HDBUY   HDBUY
4   Avatar  2009    Google  HDBUY   HDBUY

But I'm not quite sure how to aggregate it so I can get the three columns together, iTunes_Offers , Top_Platform_Offers , and Top_Platform . To group between platforms I would like to aggregate by CONCAT(Title, Year) -- for example, "Psycho (2005)" is a different movie than "Psycho (1960)".

How would I accomplish this?

Answer 1

You can use conditional aggregation:

SELECT Title, Year, Platform,
       GROUP_CONCAT(CASE WHEN platform = 'iTunes'    THEN Offer END) AS iTunes,
       GROUP_CONCAT(CASE WHEN platform = 'Microsoft' THEN Offer END) AS Microsoft,
       GROUP_CONCAT(CASE WHEN platform = 'Google'    THEN Offer END) AS Google
FROM offers
GROUP BY CONCAT(title,year);

If you could have duplicates, then use GROUP_CONCAT(DISTINCT . . .) .