Selecting max(date) twice from the same table, for different conditions - mysql

Question

This is a small snippet of my table, which currently contains ~10,000,000 rows
+---------+---------------------+-----------+----------------+
| card_id | date | avg_price | foil_avg_price |
+---------+---------------------+-----------+----------------+
| 10000 | 2014-06-28 09:05:56 | 5.02 | 10.22 |
| 20000 | 2014-06-28 09:05:54 | 14.58 | 25.10 |
| 10000 | 2014-06-29 09:05:56 | 0.00 | 19.62 |
| 20000 | 2014-06-29 09:05:54 | 14.58 | 0.00 |
| 10000 | 2014-07-01 09:05:56 | 0.00 | 19.62 |
| 20000 | 2014-07-01 09:05:54 | 0.00 | 25.10 |
+---------+---------------------+-----------+----------------+
It is a price history for cards, including what the avg_price and what the foil_avg_price was for each day or so.
I'd like to select, for a group of card id's the most recent date when the foil_avg_price was > 0, what that price was, and the most recent date that the avg_price was > 0, and what that price was. My resulting data set for the above would look something like this:
+---------+---------------------+-----------+---------------------+----------------+
| card_id | avg_date | avg_price | foil_date | foil_avg_price |
+---------+---------------------+-----------+---------------------+----------------+
| 10000 | 2014-06-28 09:05:56 | 5.02 | 2014-07-01 09:05:54 | 19.62 |
| 20000 | 2014-06-29 09:05:54 | 14.58 | 2014-07-01 09:05:54 | 25.10 |
+---------+---------------------+-----------+---------------------+----------------+
I'm sure that this involves an INNER JOIN on the same table but I can't quite get my head around it. Any help would be much appreciated.

Answer 1

Three steps:
Find last price date
Find last foil price date
resolve prices on these dates
So,
SELECT dates.*, price.avg_price, foilprice.foil_avg_price
FROM (
SELECT
card_id,
MAX(IF(avg_price>0, `date`, '0001-01-01')) AS avg_date,
MAX(IF(foil_avg_price>0, `date`, '0001-01-01')) AS foil_avg_date
FROM card_price
GROUP BY card_id
) AS dates
INNER JOIN card_price AS price
ON dates.card_id=price.`date`
INNER JOIN card_price AS foilprice
ON dates.card_id=foilprice.`date`

Answer 2

Try this query
SELECT A.card_id,max(date),MAX(avg_price), (SELECT MAX(date) FROM test WHERE card_id = A.card_id AND foil_avg_price = MAX(A.foil_avg_price)) AS date,MAX(foil_avg_price) FROM test A
GROUP BY A.card_id

Answer 3

How about if you had 20,000,000 rows...
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(card_id INT NOT NULL
,date DATETIME NOT NULL
,price_type VARCHAR(20) NOT NULL
,price_value DECIMAL(5,2) NOT NULL
,PRIMARY KEY(card_id,date,price_type)
);
INSERT INTO my_table VALUES
(10000,'2014-06-28 09:05:56','avg_price',5.02),
(20000,'2014-06-28 09:05:54','avg_price',14.58),
(10000,'2014-06-29 09:05:56','avg_price',0.00),
(20000,'2014-06-29 09:05:54','avg_price',14.58),
(10000,'2014-07-01 09:05:56','avg_price',0.00),
(20000,'2014-07-01 09:05:54','avg_price',0.00),
(10000,'2014-06-28 09:05:56','foil_avg_price',10.22),
(20000,'2014-06-28 09:05:54','foil_avg_price',25.10),
(10000,'2014-06-29 09:05:56','foil_avg_price',19.62),
(20000,'2014-06-29 09:05:54','foil_avg_price',0.00),
(10000,'2014-07-01 09:05:56','foil_avg_price',19.62),
(20000,'2014-07-01 09:05:54','foil_avg_price',25.10);
SELECT x.*
FROM my_table x
JOIN
( SELECT card_id,price_type,MAX(date) max_date FROM my_table WHERE price_value > 0 GROUP BY card_id,price_type) y
ON y.card_id = x.card_id
AND y.price_type = x.price_type
AND y.max_date = x.date;
+---------+---------------------+----------------+-------------+
| card_id | date | price_type | price_value |
+---------+---------------------+----------------+-------------+
| 10000 | 2014-06-28 09:05:56 | avg_price | 5.02 |
| 10000 | 2014-07-01 09:05:56 | foil_avg_price | 19.62 |
| 20000 | 2014-06-29 09:05:54 | avg_price | 14.58 |
| 20000 | 2014-07-01 09:05:54 | foil_avg_price | 25.10 |
+---------+---------------------+----------------+-------------+

Answer 4

Try this:
SELECT a.card_id, a.avg_date, a.avg_price, b.foil_date, b.foil_avg_price
FROM (SELECT c.card_id, c.date AS avg_date, c.avg_price
FROM cards c
INNER JOIN (SELECT c.card_id, MAX(IF(c.avg_price > 0, c.date, NULL)) avg_date
FROM cards c GROUP BY c.card_id
) a ON c.card_id = a.card_id AND c.date = a.avg_date
) AS a
LEFT JOIN (SELECT c.card_id, c.date AS foil_date, c.foil_avg_price
FROM cards c
INNER JOIN (SELECT c.card_id, MAX(IF(c.foil_avg_price > 0, c.date, NULL)) foil_date
FROM cards c GROUP BY c.card_id
) a ON c.card_id = a.card_id AND c.date = a.foil_date
) AS b ON a.card_id = b.card_id ;
OR
SELECT a.card_id, a.avg_date, a.avg_price, b.foil_date, b.foil_avg_price
FROM (SELECT *
FROM (SELECT c.card_id, c.date, c.avg_price
FROM cards c WHERE c.avg_price > 0
ORDER BY c.date DESC
) AS A
GROUP BY A.date
) AS a
LEFT JOIN ( SELECT *
FROM (SELECT c.card_id, c.date, c.foil_avg_price
FROM cards c WHERE c.foil_avg_price > 0
ORDER BY c.date DESC
) AS B
GROUP BY B.date
) AS b ON a.card_id = b.card_id;