SQL 返回所有行和计数

Question

我有 3 个表，属性个经理、地址和单位。我正在尝试使用聚合函数 COUNT 获取所有行，但它只有 returns 1 行。

我想获取 pmNo = 1 的所有地址以及每个地址的单元总数。我的 SQl 查询是这样的：

SELECT a.*, COUNT(u.unitId) AS totalUnits
FROM Units AS u
JOIN Addresses AS a ON a.addressNo = u.addressNo
JOIN PropertyManagers AS pm ON pm.pmNo = a.pmNo
WHERE pm.pmNo = 1

这给了我以下结果：

addressNo     city     province     postalCode     buildingName     pmNo     totalUnits
1             city1      prov1          V9F3b6     building1 Apt.   1            3

这是对的，但它只给了我第一个地址字段，然后将两个地址单元组合成总单元。

我想要的结果是：

addressNo     city     province     postalCode     buildingName     pmNo     totalUnits
1             city1      prov1          V9F3b6     building1 Apt.   1            2
2             city2      prov2          V0N1U8     building2 Apt.   1            1

Answer 1

COUNT 等 non-simple 案例的聚合函数需要指定发生的聚合。在您的情况下，您需要地址。由于 addressNo 是主键和唯一地址的最简单标识符，因此使用查询的 GROUP BY：

SELECT a.*, COUNT(u.unitId) AS totalUnits
FROM Units AS u
JOIN Addresses AS a ON a.addressNo = u.addressNo
JOIN PropertyManagers AS pm ON pm.pmNo = a.pmNo
WHERE pm.pmNo = 1
GROUP BY a.addressNo

SQL 返回所有行和计数

SQL returning all rows and count

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