SUM in MySQL with ORDER BY and LIMIT - php

Question

Suppose I have the following MySQL table:
I would like to know the total volume for Fuji Apples for the 3 days before the latest sale date (like a moving total). So for this example, I am after the total volume for my selection for the 3 days prior to the 04/01/14, which is 9.
I have made a number of attempts without the intended results:
SELECT sum(volume) FROM (SELECT `volume` FROM `fruit_sale_db` WHERE `fruit` = 'apple' AND `type` = 'fuji') AS subquery ORDER BY `date` DESC LIMIT 1,3
I thought ORDER BY date DESC LIMIT 1,3 would work by restricting dates to 3 starting from the second last entry but it doesn't work.

Answer 1

SELECT sum(volume) FROM `fruit_sale_db` where 'date' >= (latest_sale_date - 3) and 'date' <= latest_sale_date and `fruit` = 'apple' AND `type` = 'fuji'
and latest_sale_date would be something like
SELECT `date` FROM `fruit_sale_db` WHERE `fruit` = 'apple' AND `type` = 'fuji' ORDER BY `date` DESC LIMIT 1

Answer 2

Consider the following...
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,Fruit VARCHAR(12) NOT NULL
,Type VARCHAR(12) NOT NULL
,Date DATE NOT NULL
,Volume INT NOT NULL
);
INSERT INTO my_table (fruit,type,date,volume) VALUES
('Apple','Fuji' ,'2014-01-01',1),
('Apple','Other','2014-01-01',6),
('Apple','Fuji' ,'2014-01-01',2),
('Apple','Other','2014-01-02',1),
('Apple','Other','2014-01-02',4),
('Apple','Fuji' ,'2014-01-03',4),
('Apple','Other','2014-01-03',2),
('Apple','Fuji' ,'2014-01-04',8),
('Apple','Fuji' ,'2014-01-05',16),
('Pear' ,'Other','2014-01-06',1),
('Apple','Other','2014-01-06',4),
('Apple','Fuji' ,'2014-01-07',32),
('Apple','Other','2014-01-07',2),
('Apple','Fuji' ,'2014-01-08',64);
SELECT * FROM my_table;
+----+-------+-------+------------+--------+
| id | Fruit | Type | Date | Volume |
+----+-------+-------+------------+--------+
| 1 | Apple | Fuji | 2014-01-01 | 1 |
| 2 | Apple | Other | 2014-01-01 | 6 |
| 3 | Apple | Fuji | 2014-01-01 | 2 |
| 4 | Apple | Other | 2014-01-02 | 1 |
| 5 | Apple | Other | 2014-01-02 | 4 |
| 6 | Apple | Fuji | 2014-01-03 | 4 |
| 7 | Apple | Other | 2014-01-03 | 2 |
| 8 | Apple | Fuji | 2014-01-04 | 8 |
| 9 | Apple | Fuji | 2014-01-05 | 16 |
| 10 | Pear | Other | 2014-01-06 | 1 |
| 11 | Apple | Other | 2014-01-06 | 4 |
| 12 | Apple | Fuji | 2014-01-07 | 32 |
| 13 | Apple | Other | 2014-01-07 | 2 |
| 14 | Apple | Fuji | 2014-01-08 | 64 |
+----+-------+-------+------------+--------+
SELECT a.*
, SUM(b.volume) rolling
, GROUP_CONCAT(b.volume ORDER BY b.id DESC SEPARATOR '+' ) math
FROM my_table a
LEFT
JOIN my_table b
ON b.fruit = a.fruit
AND b.type = a.type
AND b.date BETWEEN a.date - INTERVAL 3 DAY AND a.date - INTERVAL 1 DAY
GROUP
BY a.id
ORDER
BY fruit, type, id DESC;
+----+-------+-------+------------+--------+---------+-------+
| id | Fruit | Type | Date | Volume | rolling | math |
+----+-------+-------+------------+--------+---------+-------+
| 14 | Apple | Fuji | 2014-01-08 | 64 | 48 | 32+16 |
| 12 | Apple | Fuji | 2014-01-07 | 32 | 24 | 16+8 |
| 9 | Apple | Fuji | 2014-01-05 | 16 | 12 | 8+4 |
| 8 | Apple | Fuji | 2014-01-04 | 8 | 7 | 4+2+1 |
| 6 | Apple | Fuji | 2014-01-03 | 4 | 3 | 2+1 |
| 3 | Apple | Fuji | 2014-01-01 | 2 | NULL | NULL |
| 1 | Apple | Fuji | 2014-01-01 | 1 | NULL | NULL |
| 13 | Apple | Other | 2014-01-07 | 2 | 4 | 4 |
| 11 | Apple | Other | 2014-01-06 | 4 | 2 | 2 |
| 7 | Apple | Other | 2014-01-03 | 2 | 11 | 4+1+6 |
| 5 | Apple | Other | 2014-01-02 | 4 | 6 | 6 |
| 4 | Apple | Other | 2014-01-02 | 1 | 6 | 6 |
| 2 | Apple | Other | 2014-01-01 | 6 | NULL | NULL |
| 10 | Pear | Other | 2014-01-06 | 1 | NULL | NULL |
+----+-------+-------+------------+--------+---------+-------+
http://sqlfiddle.com/#!2/5243e/1