Question

银行数据库架构：

account    (account_number, branch_name, balance) 
branch     (branch_name, branch_city, assets) 
customer   (customer_name customer_street, customer_city) 
loan       (loan_number, branch_name, amount) 
deposito   (customer_name, account_number) 
borrower   (customer_name, loan_number)

我怎么知道借款人的帐号？

Answer 1

试试这个......（根据你的评论）

SELECT c.customer_name,
  a.account_number
FROM customer c
  INNER JOIN depositor d
    ON c.customer_name = d.customer_name
  INNER JOIN borrower b
    ON d.customer_name = b.customer_name
  INNER JOIN account a
    ON a.account_number = d.account_number

请参阅DEMO

更新：

SELECT b.customer_name,
  d.account_number
FROM borrower b
  INNER JOIN depositor d
    ON d.customer_name = b.customer_name
  INNER JOIN account a
ON a.account_number = d.account_number

请参阅DEMO

Answer 2

根据您的评论，customers似乎通过accounts表格与depositor相关联。如果是这样，那么你可以使用：

select c.customer_name,
  a.account_number,
  a.balance
from customer c
inner join depositor d
  on c.customer_name = d.customer_name
inner join account a
  on d.account_number = a.account_number

请参阅SQL Fiddle with Demo

如果您想知道借款人的帐号，那么您将在borrower表中添加一个JOIN：

select c.customer_name,
  a.account_number,
  a.balance
from customer c
inner join depositor d
  on c.customer_name = d.customer_name
inner join account a
  on d.account_number = a.account_number
inner join borrower b
  on c.customer_name = b.customer_name

您的数据库设计似乎有一些问题。根据您当前的结构，如果您想了解borrowers，则必须加入depositor以获取帐号或loan表以将贷款与帐户相关联

如果您加入loan表，则查询将为：

select b.customer_name,
  a.account_number
from borrowers b
inner join loan l
  on b.loan_number = l.loan_number
inner join account a
  on l.branch_number = a.branch_number

但问题是loan表只能在account加入branch_number，此分支号码将与多个帐户相关联。您应该有一个列，用于标识每个borrower的{{1}}，因为缺少此列，您目前无法找到每个借款人的帐号。

加入2个不同列的表

2 个答案: