如何进行这些 JOIN 查询？

Question

我正在处理一些关于我的作业的问题，我们将不胜感激。

1. 列出分支机构以及员工人数和分配给他们的客户、总贷款金额、总账户余额、位于给定城市的分支机构的资产。
2. 列出在给定时间段内进行账户和贷款操作的客户
3. 列出员工以及在给定时间段内每个客户服务的人数

我想一个简单的例子就足够我解决休息了。

这是我迄今为止尝试的第一个：

ALTER PROCEDURE [dbo].[SelecBranchesByCity]
    (@City varchar(50))
AS
    select
        Br.Name as BranchName,
        COUNT(emps.ID) as NumberOfEmployee,
        SUM(emps.NumberOfCustomers) as TotalCustomers,
        SUM(lo.Amount) as TotalAmountOfLoan,
        SUM(acc.Balance) as TotalBalance,
        Br.Assets as Assets
    from Branches Br
    left outer join Employees emps on emps.[BranchName] = Br.Name
    left outer join Loans lo on lo.[BranchName] = Br.Name
    left outer join Accounts acc on acc.[BranchName] = Br.Name
    where
        Br.[Address] like '%'+@City+'%'
    GROUP BY
        Br.ID,
        Br.Name,
        Br.Assets

这是架构！

Answer 1

架构令人恐惧。多对多客户贷款？客户帐户上的多对多？为什么？？员工有一个branchname 列，而不是与branches 的FK 关系。 loan_operations 对 employees 有 FK！？我并不是要偏离主题或听起来轻率，但是这里有很多反模式，我什至不知道从哪里开始。但无论如何，我会尽力帮助解决具体问题。

第一季度：

CREATE PROCEDURE GetBranchSummaryByCity
    @City varchar(50)
AS
SELECT
    b.id, b.address, b.name, b.assets,
    b2.EmployeeCount, b2.CustomerCount,
    b2.TotalLoanAmount, b2.TotalAccountBalance
FROM branches b
INNER JOIN
(
    SELECT
        b.id,
        ISNULL(COUNT(DISTINCT e.id), 0) AS EmployeeCount,
        ISNULL(COUNT(c.id), 0) AS CustomerCount,
        ISNULL(SUM(l.amount), 0) AS TotalLoanAmount,
        ISNULL(SUM(a.balance), 0) AS TotalAccountBalance
    FROM branches b
    LEFT JOIN employees e
        -- Fix your schema so this matches the branch ID instead!
        ON e.branchname = b.name
    LEFT JOIN employee_customer ec
        ON ec.employeeid = e.id
    LEFT JOIN customers c
        ON c.id = ec.customerid
    LEFT JOIN customer_accounts ca
        ON ca.customerid = c.id
    LEFT JOIN accounts a
        ON a.id = ca.accountid
    LEFT JOIN loan_customer lc
        ON lc.customerid = c.id
    LEFT JOIN loans l
        ON l.id = lc.loanid
    WHERE b.Name LIKE '%' + @City + '%'
    GROUP BY b.id
) b2
ON b2.id = b.id

我会注意到您在loans 和loan_operations 中都有一个amount 列。很难知道这两者之间有什么区别 - loans 完全有可能根本不应该有这个列，而是应该从 loan_operations 的列中求和。

第二季度：

CREATE PROCEDURE FindCustomersWithLoansByDateRange
    @BeginDate datetime,
    @EndDate datetime
AS
SELECT c2.id, c2.name, c2.address, ...
FROM
(
    SELECT DISTINCT c.id
    FROM customers c
    INNER JOIN loan_customer lc
        ON lc.customerid = c.id
    INNER JOIN loans l
        ON l.id = lc.loanid
    INNER JOIN loan_operations lo
        ON lo.loanid = l.id
    WHERE lo.date BETWEEN @BeginDate AND @EndDate
) c1
INNER JOIN customers c2
ON c2.id = c1.id

第三季度：

CREATE PROCEDURE GetEmployeeServiceSummaryByDateRange
    @BeginDate datetime,
    @EndDate datetime
AS
SELECT e.id, ISNULL(es.CustomerCount, 0) AS CustomerCount, e.name, e.position, ...
FROM employees e
LEFT JOIN
(
    SELECT e.id, COUNT(DISTINCT c.id) AS CustomerCount
    FROM employees e
    INNER JOIN employee_customer ec
        ON ec.employeeid = e.id
    INNER JOIN customers c
        ON c.id = ec.customerid
    INNER JOIN loan_customer lc
        ON lc.customerid = c.id
    INNER JOIN loans l
        ON l.id = lc.loanid
    INNER JOIN loan_operations lo
        ON lo.loanid = l.id
    WHERE lo.date BETWEEN @BeginDate AND @EndDate
    GROUP BY e.id
) es
ON es.id = e.id