多行MySQL查詢與「哪裏」的原因？

Question

產品表：

id | name 
100 A 
101 B 
102 C 

產品分類表：

id | product_id | category_id 
1 100   7 
2 100   5 
3 101   7 
4 101   2 
5 102   7 
6 102   10 

我怎樣才能得到的product_id，它的CATEGORY_ID已經得到7和2？

Answer 1

要讓有2類和7個產品都那麼你可以這樣做

select p.* 
from products p 
join ProductCategory c on(p.id = c.product_id) 
where c.category_id in(2,7) 
group by p.id 
having count(distinct c.category_id) = 2 

爲了有有2類或7，則產品你可以這樣做

select distinct p.* 
from products p 
join ProductCategory c on(p.id = c.product_id) 
where c.category_id in(2,7) 

Answer 2

如何我可以得到product_id，它的category_id有7和2嗎？

SELECT product_id 
FROM ProductCategory 
WHERE category_id IN (2, 7) 
GROUP BY product_id 
HAVING count(DISTINCT category_id) = 2