我将在此处使用聚合：

SELECT c.customer_ID 
FROM customer c
INNER JOIN transactions t
    ON t.customer_ID = c.customer_ID
INNER JOIN transaction_contains tc
    ON tc.transaction_ID = t.transaction_ID
INNER JOIN product p
    ON tc.UPC = p.UPC
WHERE
    p.brand IN ('Pepsi', 'Coca-Cola')
GROUP BY
    c.customer_ID
HAVING
    COUNT(DISTINCT p.brand) = 2;

请注意，我还使用了现代显式内部联接。

像这样的事情应该马上就能做到。

SELECT
    DISTINCT(c1.Customer_ID)
FROM
    Customer c1
JOIN Transactions t ON t.Customer_ID = c1.Customer_ID
JOIN Contain c2 ON c2.Transaction_ID = t.Transaction_ID
JOIN Products p ON p.UPC = c2.UPC
WHERE
    p.Brand IN ('Pepsi', 'Coca-Cola');

您可以使用group by来实现这一点。如果您在IN中选择2个产品，那么您的计数必须是2。我使用了ANSI SQL标准语法进行连接

select  
  C1.customer_ID 
from 
  customer as C1 inner join 
  transactions as T1 on C1.customer_ID = T1.customer_ID  inner join 
  transaction_contains as T2 on T1.transaction_ID = T2.transaction_ID inner join
  product P on p.upc = T2.upc  
where 
  p.Brand IN ('Pepsi', 'Coca-Cola')
Group by 
  C1.customer_ID 
having 
  count(*) = 2

根据语法验证器检查语法