在mysql中使用内部联接复制值

我有3张表，我想得到总数，但我没有得到正确的结果

第一表（投资者）

第二表（付款）

第三张表（账单）

这是我的问题

SELECT SUM(billed.billed)
FROM billed AS billed
INNER JOIN payments AS payments ON billed.payments_id = payments.id
INNER JOIN investors AS investors ON payments.investor_id = investors.investor_id

我得到的结果不是

1689

，而是

2178

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我真的被我的答案难住了，真的有办法只使用查询就可以做到这一点吗？

如果您只需要账单的总金额，只需直接查询该表，无需加入：

SELECT SUM(billed) FROM billed

如果出于某种原因您需要加入，我将在子查询中选择不同的投资者，然后加入它：

SELECT SUM(billed.billed)
FROM billed AS billed
INNER JOIN payments AS payments ON billed.payments_id = payments.id
INNER JOIN (SELECT DISCTINCT investors FROM investors) AS investors ON payments.investor_id = investors.investor_id

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我需要使用JOIN，因为账单金额将取决于investor表。欢迎@JanessaBautista！如果我的回答正确回答了你的问题，请点击绿色的复选标记。。。谢谢见：

SELECT SUM(billed.billed)
FROM billed AS billed
INNER JOIN payments AS payments ON billed.payments_id = payments.id
INNER JOIN investors AS investors ON payments.investor_id = investors.investor_id

SELECT SUM(billed) FROM billed

SELECT SUM(billed.billed)
FROM billed AS billed
INNER JOIN payments AS payments ON billed.payments_id = payments.id
INNER JOIN (SELECT DISCTINCT investors FROM investors) AS investors ON payments.investor_id = investors.investor_id