Question

我有一些表格：

“branch”表（branch_name，branch_city，assets）

“customer”表（customer_name，customer_street，customer_city）

“account”表（account_number，branch_name，balance）

“贷款”表（loan_number，branch_name，金额）

“存款人”表（customer_name，account_number）

“借款人”表（customer_name，loan_number）

现在，我想查找在布鲁克林所有分行拥有帐户的所有客户。这是我的SQL问题。但我想知道如何使用TABLE JOIN，并且不使用EXCEPT来解决这个问题。能有人帮我吗？谢谢。

SELECT distinct S.customer_name FROM depositor as S
WHERE not exists (
     (SELECT branch_name
      FROM branch
      WHERE branch_city = 'Brooklyn')
      EXCEPT
      (SELECT R.branch_name
       FROM depositor as T, account as R
       WHERE T.account_number = R.account_number and
             S.customer_name = T.customer_name ))

Answer 1

Select A.customer_name
From depositor as A
Left join account as B
on B. account_number = A.account_number
group by A.customer_name
Having count(distinct(B.branch_name))  = 
(select count(branch_name) from branch where branch_city = 'Brooklyn')

Answer 2

我无法想出使用UNION执行此操作的方法。您的问题是找到一个在布鲁克林拥有所有分支机构的客户。从根本上说，有两种方法可以解决这个问题。

解决方案1 - 查找不的客户在布鲁克林拥有所有分支机构。

（故意双重否定）。换句话说，找到所有在布鲁克林没有至少一个分支机构的客户，然后完成其余的工作。

这就是你在你的例子中所做的。你把布鲁克林的所有分支机构EXCEPT带到了客户所拥有的分支机构，如果没有布鲁克林分支机构，那么客户就拥有了所有分支机构。您可以使用连接以另一种方式执行此操作，但您的可能性更高。

SELECT customer_name
FROM customer
WHERE customer_name NOT IN (
    SELECT d.customer_name
    FROM depositor d
    INNER JOIN branch brooklyn ON brooklyn.branch_city = 'Brooklyn'
    LEFT JOIN account a 
        ON d.account_number = a.account_number
        AND brooklyn.branch_name = a.branch_name 
    WHERE a.account_number IS NULL )

解决方案2 - 查找布鲁克林分店数量与布鲁克林分行数相同的所有客户。

为了做到这一点，您需要使用GROUP BY来获取每位客户的布鲁克林分行数，然后您可以使用它来与布鲁克林分行的总数进行比较。

SELECT d.customer_name
FROM depositor d
INNER JOIN account a ON d.account_number = a.account_number
INNER JOIN branch b ON a.branch_name = b.branch_name
WHERE b.branch_city = 'Brooklyn'
GROUP BY d.customer_name
HAVING COUNT(DISTINCT B.branch_name) = (
    SELECT COUNT(branch_name)
    FROM branch 
    WHERE branch_city = 'Brooklyn')

UNION用于组合两个数据集。如果你的问题是......

＆＃34;查找所有拥有布鲁克林分行帐户或贷款的客户。＆＃34;

...然后你可以使用UNION。

SELECT DISTINCT d.customer_name
FROM depositor d
INNER JOIN account a ON d.account_number = a.account_number
INNER JOIN branch b ON a.branch_name = b.branch_name
WHERE b.branch_city = 'Brooklyn'
UNION
SELECT DISTINCT l.customer_name
FROM borrower bo
INNER JOIN loan l ON bo.loan_number = l.loan_number
INNER JOIN branch b ON l.branch_name = b.branch_name
WHERE b.branch_city = 'Brooklyn'

Answer 3

假设您想要答案：＆＃34;找到所有在布鲁克林任何分行拥有帐户的客户＆＃34;

select c.*
from customer c
inner join depositor d
   on c.customer_name = d.customer_name
inner join account a
   on d.account_numver = a.account_number
inner join branch b
   on a.branch_name = b.branch_name
where b.branch_city = 'Brooklyn'

如果客户可以拥有多个帐户，或者某个帐户可以拥有多个分支，则需要调整联接。

查找位于布鲁克林所有分支机构的所有客户

3 个答案: