Problem Description
I have a table of player performance:
```
CREATE TABLE TopTen (
id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
home INT UNSIGNED NOT NULL,
`datetime`DATETIME NOT NULL,
player VARCHAR(6) NOT NULL,
resource INT NOT NULL
);
```
What query will return the rows for each distinct `home` holding its maximum value of `datetime`? In other words, how can I filter by the maximum `datetime` (grouped by `home`) and still include other non-grouped, non-aggregate columns (such as `player`) in the result?
For this sample data:
```
INSERT INTO TopTen
(id, home, `datetime`, player, resource)
VALUES
(1, 10, '04/03/2009', 'john', 399),
(2, 11, '04/03/2009', 'juliet', 244),
(5, 12, '04/03/2009', 'borat', 555),
(3, 10, '03/03/2009', 'john', 300),
(4, 11, '03/03/2009', 'juliet', 200),
(6, 12, '03/03/2009', 'borat', 500),
(7, 13, '24/12/2008', 'borat', 600),
(8, 13, '01/01/2009', 'borat', 700)
;
```
the result should be:
| id | home| datetime | player | resource |
|----|-----|------------|--------|----------|
| 1 | 10 | 04/03/2009 | john | 399 |
| 2 | 11 | 04/03/2009 | juliet | 244 |
| 5 | 12 | 04/03/2009 | borat | 555 |
| 8 | 13 | 01/01/2009 | borat | 700 |
I tried a subquery getting the maximum `datetime` for each `home`:
-- 1 ..by the MySQL manual:
SELECT DISTINCT
home,
id,
datetime AS dt,
player,
resource
FROM TopTen t1
WHERE `datetime` = (SELECT
MAX(t2.datetime)
FROM TopTen t2
GROUP BY home)
GROUP BY `datetime`
ORDER BY `datetime` DESC
The result-set has 130 rows although database holds 187, indicating the result includes some duplicates of `home`.
Then I tried joining to a subquery that gets the maximum `datetime` for each row `id`:
-- 2 ..join
SELECT
s1.id,
s1.home,
s1.datetime,
s1.player,
s1.resource
FROM TopTen s1
JOIN (SELECT
id,
MAX(`datetime`) AS dt
FROM TopTen
GROUP BY id) AS s2
ON s1.id = s2.id
ORDER BY `datetime`
Nope. Gives all the records.
I tried various exotic queries, each with various results, but nothing that got me any closer to solving this problem.
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