select customer_name, borrower.loan_number, amount from borrower, loan where borrower.loan_number = loan.loan_number and branch_name = 'Perryridge’. What is the meaning of the borrower.loan_number = loan.loan_number。请用中文解释

"borrower.loan_number = loan.loan_number" 是一个连接条件。它指定了如何将 "borrower" 表和 "loan" 表连接起来以从两个表中检索数据。

具体来说，它表示应该将 "borrower" 表中的 "loan_number" 列与 "loan" 表中的 "loan_number" 列进行比较，只有这些值匹配的行才会包含在结果集中。换句话说，这个条件确保只返回从 "Perryridge" 分行借贷的客户的姓名、贷款编号和贷款金额。

相关问题

select distinct customer_name from borrower, loan where borrower.loan_number = loan.loan_number and branch_name = 'Perryridge' and (branch_name, customer_name ) in( select branch_name, customer_name from depositor, account where depositor.account_number = account.account_number )

这是一个 SQL 查询语句，目的是查找在 Perryridge 分行有存款账户的所有客户姓名。具体解释如下：

首先，使用 inner join 连接 borrower 表和 loan 表，以获取所有在 Perryridge 分行有贷款的客户信息。

然后，在 inner join 的结果集上再次使用 inner join 连接 depositor 表和 account 表，以获取所有在 Perryridge 分行有存款账户的客户信息。

最后，使用 select distinct 语句去重并只返回客户姓名。

已知银行企业的数据库由以下表组成： ①分行表 branch(branch-name, branch-city, assets) ②客户表 customer(customer-name , customer-street, customer-city ) ③贷款明细表 loan(loan-number, branch-name, amount) ④客户贷款表 borrower(customer-name, loan-number) ⑤存款明细表 account(account-number, branch-name, balance ) ⑥客户存款表 depositor(customer-name, account-number) 注：带下划线的属性为主码，假设客户的名字不相同 完成如下操作： （1）用SQL语句创建表。 （2）使用关系代数和SQL语句找出在Brighton银行中有存款的所有客户的姓名、存款号、和存款额。 （3）使用关系代数和SQL语句找出账户平均余额小于5000元的支行，显示支行名称及账户平均余额。 （4）使用关系代数和SQL语句找出所有在银行中有贷款但无账户的客户。 （5）使用关系代数和SQL语句对所有存款余额大于平均存款额的账户付3%的利息。

很抱歉，我是一个自然语言处理AI，无法直接执行SQL语句或关系代数操作。但我可以给你提供一些参考：

（1）用SQL语句创建表。

CREATE TABLE branch (
  branch_name VARCHAR(255) PRIMARY KEY,
  branch_city VARCHAR(255),
  assets DECIMAL(10,2)
);

CREATE TABLE customer (
  customer_name VARCHAR(255) PRIMARY KEY,
  customer_street VARCHAR(255),
  customer_city VARCHAR(255)
);

CREATE TABLE loan (
  loan_number INT PRIMARY KEY,
  branch_name VARCHAR(255),
  amount DECIMAL(10,2)
);

CREATE TABLE borrower (
  customer_name VARCHAR(255),
  loan_number INT,
  PRIMARY KEY (customer_name, loan_number),
  FOREIGN KEY (customer_name) REFERENCES customer(customer_name),
  FOREIGN KEY (loan_number) REFERENCES loan(loan_number)
);

CREATE TABLE account (
  account_number INT PRIMARY KEY,
  branch_name VARCHAR(255),
  balance DECIMAL(10,2)
);

CREATE TABLE depositor (
  customer_name VARCHAR(255),
  account_number INT,
  PRIMARY KEY (customer_name, account_number),
  FOREIGN KEY (customer_name) REFERENCES customer(customer_name),
  FOREIGN KEY (account_number) REFERENCES account(account_number)
);

（2）使用关系代数和SQL语句找出在Brighton银行中有存款的所有客户的姓名、存款号、和存款额。

关系代数：

$$\pi_{customer\_name, account\_number, balance}(\sigma_{branch\_name='Brighton'}(depositor \bowtie account))$$

SQL语句：

SELECT customer_name, account_number, balance
FROM depositor
JOIN account ON depositor.account_number = account.account_number
WHERE account.branch_name = 'Brighton';

（3）使用关系代数和SQL语句找出账户平均余额小于5000元的支行，显示支行名称及账户平均余额。

关系代数：

$$\pi_{branch\_name,avg(balance)}(\rho_{account2}(account) \bowtie_{account1.branch\_name = account2.branch\_name} \gamma_{account1.branch\_name,avg(balance)}(account as account1))$$

$$\sigma_{avg(balance) < 5000}(account2)$$

SQL语句：

SELECT account1.branch_name, AVG(account2.balance) AS avg_balance
FROM account AS account1
JOIN account AS account2 ON account1.branch_name = account2.branch_name
GROUP BY account1.branch_name
HAVING AVG(account2.balance) < 5000;

（4）使用关系代数和SQL语句找出所有在银行中有贷款但无账户的客户。

关系代数：

$$\pi_{customer\_name}(\sigma_{borrower.loan\_number = loan.loan\_number \land account.branch\_name \text{ is null}}(borrower \bowtie loan \bowtie account))$$

SQL语句：

SELECT borrower.customer_name
FROM borrower
JOIN loan ON borrower.loan_number = loan.loan_number
LEFT JOIN account ON loan.branch_name = account.branch_name
WHERE account.account_number IS NULL;

（5）使用关系代数和SQL语句对所有存款余额大于平均存款额的账户付3%的利息。

关系代数：

$$account' \leftarrow \sigma_{balance > avg(balance)}(account)$$

$$account' \leftarrow \rho_{account2}(account')$$

$$account' \leftarrow account' \cup \gamma_{avg(balance)}(account')$$

$$account' \leftarrow \rho_{account3}(account')$$

$$account' \leftarrow account' \bowtie_{account2.branch\_name = account3.branch\_name}(account2 \times account3)$$

$$account' \leftarrow \sigma_{interest\_rate = 0.03}(account')$$

$$account \leftarrow account \cup account'$$

SQL语句：

UPDATE account
SET balance = balance * 1.03
WHERE balance > (SELECT AVG(balance) FROM account);