Question

我有以下表格：

人：

PersonID(PK)
AppartmentID(FK)
Name

Appartments公寓：

AppartmentID(PK)
BuildingID(FK)
ApartmentNumber

建筑物：

BuildingID
Address

我想知道每栋楼里有多少人居住，就像那样：

| Address  | Sum |
|----------|-----|
| Address1 | 169 |
| Address2 | 353 |
| Address3 | 232 |
| Address4 | 199 |

到目前为止，我得到的最佳查询是：

SELECT 
   Buildings.BuildingID,
   sum(c)
FROM
   (SELECT 
        COUNT(*) as c 
    FROM 
        Persons
    GROUP BY 
        Persons.AppartmentID) as c, Appartments
GROUP BY 
    Buildings.BuildingID;

但它没有像我期望的那样工作。

非常感谢任何帮助。

Answer 1

SELECT b.BuildingID, 
       b.Address, 
       count(p.personID) as persons
FROM Buildings b
LEFT JOIN Appartments a ON a.BuildingID = b.BuildingID
INNER JOIN Persons p ON p.AppartmentID = a.AppartmentID
GROUP BY b.BuildingID, b.Address

SQL查询中的COUNT（）的SUM（）

1 个答案: