SQL：如何根据两个不同的条件对相同的值求和

Question

假设我有以下 table 记录谁投资了公司列表。

Table: corporate_investments

company investor investment date
--------------------------------
CorpA    Alice     10       12/1
CorpB    Bob       20       12/2
CorpB    Sally     20       12/3 
CorpC    Cathy     30       12/4
CorpC    Alice     40       12/5
CorpC    Bob       10       12/6
CorpC    Bob       20       12/7

我如何运行查询 returns 每家公司、Bob（他是 VIP）的总投资以及对该公司的总投资？

我试过了

SELECT company,SUM(investment) as total investment
FROM corporate_investments
GROUP BY company

成功找到投资总额。

company    total_investment
---------------------------
CorpA           10
CorpB           40
CorpC          100

现在我想为每个公司添加 Bob 的总金额。我需要 SUM() 函数本身中的子句之类的东西，但我不知道如何做到这一点。

Answer 1

使用条件聚合：

SELECT company, SUM(investment) as total,
       sum(case when investor = 'Bob' then investment else 0 end) as BobTotal
FROM corporate_investments
GROUP BY company;

Answer 2

您可以使用 WITH ROLLUP:

获得每个投资者的滚动总数

SELECT company, investor, SUM(investment) AS total
FROM corporate_investments
GROUP BY company, investor WITH ROLLUP

这会产生这样的结果：

CorpA    Alice     10
CorpA    NULL      10
CorpB    Bob       20
CorpB    Sally     20
CorpB    NULL      40
CorpC    Alice     40
CorpC    Bob       30
CorpC    Cathy     30
CorpC    NULL     100

SQL：如何根据两个不同的条件对相同的值求和

SQL: How to SUM the same value on two different criteria

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