Question

我有两张桌子

Table1 (Users)
ID,   NAME,        COUNTRY
1,    Joe Bloggs,  1
2,    Joe Jnr,     1
3,    Joe Snr,     2

Table2 (Orders)
UsersID,  Product
1,        Apple TV
1,        iPad Pro
1,        MacBook Pro
2,        iPad Mini
2,        iPad Pro
3,        iPad Air
3,        iPad Pro

如果我想要一个产品列表，如果用户居住在Country = 1

Select Orders.Product from users left join Users.ID = ORDERS.ID WHERE COUNTRY = 1

工作正常

如果我想要一个产品列表，如果用户居住在country = 1并带来macbook Pro（但没有在列表中显示macbook pro），该怎么办？

所以只需显示

AppleTV 
iPAD pRO

Answer 1

在经典SQL中编写一个分层子选择。应该有效的代码：

    Select Product from Orders
Where Product <> 'MacBook Pro'  -- you don't want MacBook Pro in results
and UsersID in
(Select ID from Users
 where country = '1'   --get all Country 1 users that Purchased MacBooks
 and ID in
 (Select B.UsersID
  from Orders B  --- aliased for clarity
  where  Product = 'MacBook Pro'))

Answer 2

快速回答这个问题很简单。首先，选择购买MacBook Pro的用户以及居住在该国家/地区的用户：

SELECT T_USERS.id
FROM Users T_USERS INNER JOIN Orders T_ORDERS
ON (T_USERS.id = T_ORDERS.UsersID)
WHERE T_USERS.Country = 1
    AND T_ORDERS.product = 'MacBook Pro'

然后，在子查询中使用它来获取用户并避免包含MacBook产品的行：

SELECT Product 
FROM   Orders 
WHERE  product <> 'MacBook Pro' 
       AND UsersID IN (SELECT T_USERS.id 
                       FROM   Users T_USERS  INNER JOIN Orders T_ORDERS 
                       ON ( T_USERS.id = T_ORDERS.UsersID ) 
                       WHERE  T_USERS.country = 1 
                              AND T_ORDERS.product = 'MacBook Pro')

它运作得很好。

Answer 3

        Select distinct o1.Product 
        from Orders o1
        inner join Orders o2
        on o1.UserId = o2.UserId
        and o2.Product = 'MacBook Pro'
        inner join Users u
        on o1.UserId = u.Id
        where o1.Product <> 'MacBook Pro'
        and u.country = 1
        order by o1.Product

SQL一对多条件问题

3 个答案: