在選擇語句中檢查多個值

Question

給定一個具有這樣的銷售額的表：

| PRODUCT_ID | USER_ID |
|------------|---------|
|          1 |       1 |
|          2 |       1 |
|          3 |       1 |
|          3 |       2 |
|          4 |       2 |
|          1 |       3 |
|          3 |       3 |

以及帶有產品和制造商的表格，如下所示：

| PRODUCT_ID | MANUFACTURER_ID |
|------------|-----------------|
|          1 |               1 |
|          2 |               1 |
|          3 |               2 |
|          4 |               2 |

如何找到從制造商那里購買了所有產品的用戶？ 我知道我可以用

SELECT *
FROM product
WHERE MANUFACTURER_ID = x

確定哪些產品屬於制造商x，但我不知道如何從那里繼續。

Answer 1

這會選擇不存在某個制造商尚未購買的產品的所有用戶-因此，他們已經購買了該制造商的所有產品。

select t1.user_id from (
    select user_id from sales s 
    join manufacturers m on s.product_id = m.product_id
    where manufacturer_id = x
    group by user_id
) t1 where not exists (
    select 1 from manufacturers m
    left join sales s on s.product_id = m.product_id and s.user_id = t1.user_id
    where m.manufacturer_id = t1.manufacturer_id       
    and s.product_id is null    
)

編輯

另一種方法是選擇已購買所有產品的所有用戶

select t1.user_id from (
    select s.user_id, count(*) cnt from product p
    join sales s on s.product_id = p.product_id
    where p.manufacturer_id = x
    group by s.user_id
) t1 join (
    select count(*) cnt from product 
    where manufacturer_id = x
) t2 on t2.cnt = t1.cnt

Answer 2

我會這樣寫查詢：

select s.user_id
from sales s join
     products p
     on s.product_id = p.product_id
where p.manufacturer_id = x
group by s.user_id
having count(distinct s.product_id) = (select count(*)
                                       from products
                                       where manufacturer_id = x
                                      );