MySQL查询组合来自多个表的总和

Question

我有以下查询，它试图生成所有客户、他们的项目、每个项目花费的时间、发票总额和发票总数的列表。

SELECT
    c.name as client,
    p.name as project,
    SUM(t.hours) as hours,
    SUM(ci.amount) as invoice_amount,
    COUNT(ci.id) as number_invoices
FROM
    projects p
    INNER JOIN client_master c ON c.harvest_id = p.client_id
    INNER JOIN timesheet t ON t.project_id = p.id 
    LEFT OUTER JOIN projects_contracts pc ON pc.project_id = p.id
    INNER JOIN contracts_invoices ci ON ci.contract_id = pc.contract_id
GROUP BY
    c.name,
    p.name
ORDER BY
    c.name, 
    p.name,
    t.hours

当我运行查询时，“小时数”计算正确，但 invoice_amount 和 number_invoices 的总和/计数并没有根据上下文加入到项目中，而是加入到表中的发票总数中。如果我注释掉 sum() 中的一个，那么我会得到正确的值，但当它们都在时不会。

预期结果

客户 A，项目 1, 1000, $10,000, 2

客户 A，项目 2，5000，5000 美元，1

客户 B，项目 1，100，3000 美元，1

实际结果

客户 A，项目 1, 1000, $150,000, 20

客户 A，项目 2, 5000, $50,000, 81

客户 B，项目 1, 100, $83000, 12

我尝试过使用 grouping 和 join 语句，但没有成功。有什么简单的我忽略了还是需要完全重写？

Answer 1

由于发票依赖于合同，而合同是可选的（左连接）， 使该联接也成为左联接。

SELECT
    c.name as client,
    p.name as project,
    SUM(t.hours) as hours,
    SUM(ci.amount) as invoice_amount,
    COUNT(ci.id) as number_invoices
FROM
    projects p
    INNER JOIN client_master c 
        ON c.harvest_id = p.client_id
    INNER JOIN timesheet t 
        ON t.project_id = p.id 
    LEFT JOIN projects_contracts pc 
        ON pc.project_id = p.id
    LEFT JOIN contracts_invoices ci 
        ON ci.contract_id = pc.contract_id
GROUP BY
    c.name,
    p.name
ORDER BY
    c.name, 
    p.name,
    t.hours

Answer 2

这可能不是最好的方法，但我敢打赌它有效

SELECT
    c.name as client,
    p.name as project,
    t.hours as hours,
    ci.amount as invoice_amount,
    ci.count as number_invoices
FROM
    projects p
    INNER JOIN client_master c 
        ON c.harvest_id = p.client_id
    INNER JOIN (SELECT project_id, SUM(hours) AS hours FROM timesheet GROUP BY project_id) t
        ON t.project_id = p.id 
    LEFT OUTER JOIN projects_contracts pc 
        ON pc.project_id = p.id
    LEFT OUTER JOIN (SELECT contract_id, SUM(amount) AS amount, COUNT(DISTINCT id) AS count FROM contracts_invoices GROUP BY contract_id) ci
        ON ci.contract_id = pc.contract_id
GROUP BY
    c.name,
    p.name
ORDER BY
    c.name, 
    p.name,
    t.hours