SQL Server 同一查询中的多个计数 - CosmosDB

Question

我想创建一个查询，计算下面描述的文档集合中的喜欢和不喜欢的总数。

{
    "id": "403031b7-a1b6-4e08-9d82-360bb41b97cd",
    "car_id": "0839404d5bc4140f28abfd19329b0ebc",
    "created": 1621881785,
    "type": "like",
    "version": 1,
    "fingerprint": "kHqPGWS1Mj18sZFsP8Wl",
}

{
    "id": "403031b7-a1b6-4e08-9d82-360bb41b97cd",
    "car_id": "0839404d5bc4140f28abfd19329b0ebc",
    "created": 1621881785,
    "type": "unlike",
    "version": 1,
    "fingerprint": "kHqPGWS1Mj18sZFsP8Wl",
}

---

以下内容非常适合一次计数：

SELECT COUNT(1) AS likes from cars c WHERE c.type="like" and c.car_id="0839404d5bc4140f28abfd19329b0ebc"

但我想在同一查询中计算 c.type 为“like”和 c.type="unlike" 的展位喜欢和不喜欢。

---

结果如下：

{
    "likes": a,
    "unlikes": b
}

Answer 1

您可以使用条件聚合：

SELECT SUM(CASE WHEN c.type = 'like' THEN 1 ELSE 0 END) AS likes,
       SUM(CASE WHEN c.type = 'unlike' THEN 1 ELSE 0 END) as unlikes
FROM cars c
WHERE c.car_id = '0839404d5bc4140f28abfd19329b0ebc';

或者使用聚合：

select c.type, count(*)
from cars c
where c.car_id = '0839404d5bc4140f28abfd19329b0ebc'
group by c.type;