Det du skal arbejde med er, om garantien stadig er gyldig eller udløbet og garantidatoen, så du skal først bygge en tabel, der afspejler det:
select product
, IF( warranty >= NOW(), 1, 0 ) as valid
, IF( warranty < NOW(), 1, 0 ) as expired
, warranty as last
from (
select product
, ADDDATE( purchased, INTERVAL 5 YEAR ) as warranty
from productWarranty
) w
group by product
;
Det ville give dig sådan noget:
+---------+-------+---------+---------------------+
| product | valid | expired | warranty |
+---------+-------+---------+---------------------+
| Hammer | 1 | 0 | 2017-01-01 00:00:00 |
| Nipper | 1 | 0 | 2017-01-01 00:00:00 |
| Nipper | 1 | 0 | 2017-01-01 00:00:00 |
| Nipper | 1 | 0 | 2017-01-01 00:00:00 |
| Saw | 1 | 0 | 2017-01-01 00:00:00 |
| Saw | 0 | 1 | 2011-01-01 00:00:00 |
| Saw | 1 | 0 | 2017-01-01 00:00:00 |
| Saw | 1 | 0 | 2017-01-01 00:00:00 |
+---------+-------+---------+---------------------+
Brug derefter aggregerede funktioner til at filtrere og opsummere de oplysninger, du leder efter:
select product
, SUM( IF( warranty >= NOW(), 1, 0 ) ) as valid
, SUM( IF( warranty < NOW(), 1, 0 ) ) as expired
, MAX( warranty ) as last
from (
select product
, adddate( purchased, interval 5 year ) as warranty
from productWarranty
) w
group by product
;
+---------+-------+---------+---------------------+
| product | valid | expired | last |
+---------+-------+---------+---------------------+
| Hammer | 1 | 0 | 2017-01-01 00:00:00 |
| Nipper | 3 | 0 | 2017-01-01 00:00:00 |
| Saw | 3 | 1 | 2017-01-01 00:00:00 |
+---------+-------+---------+---------------------+