复杂的Postgres查询 [英] Complex Postgres query

问题描述

我具有以下数据库模式-

I have a db schema like following -

(Country table)
| Country | Country Code| 
-------------------------
    ABC         A 
    BCD         B

（组织结构表）

Org 1            A                O1
Org 2            B                O2
Org 3            A                O3

（交易记录表）

 O1             X1                Y1
 O2             X2                Y2
 O3             X3                Y3

我希望结果集像这样-

| Corridor | Total Export | Total Import |
------------------------------------------
  ABC-BCD      X1+X2+X3       Y1+Y2+Y3

走廊列应为所有组合

如何构成查询以实现此逻辑？谢谢

How can I form a query to implement this logic? Thanks

推荐答案

所有您需要做的就是运行汇总查询：

All you need to do is to run an aggregate query:

select sum(t.export) as TotalExport,
sum(t.import) as TotalImport
FROM country c inner join Organization o on c.Country_Code = o.Country_Code
inner join Transaction t on o.organization_code = t.organization_code 

您问：走廊列在哪里？答案是：使用 string_agg 函数：

Now, you ask: where is the Corridor column? The answer is: use the string_agg function:

select string_agg(DISTINCT c.country, '-' ORDER BY c.country) as Corridor,
sum(t.export) as TotalExport,
sum(t.import) as TotalImport
FROM country c inner join Organization o on c.Country_Code = o.Country_Code
inner join Transaction t on o.organization_code = t.organization_code 

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