SQL Server 查询 COUNT NULL/Blank 值和 GROUP BY

Question

我一直试图解决这个问题，但没有成功。我有一个名为Appraisal 的表，其中有一列StatusID。我需要计算按StatusId 分组的评估数量。 Appraisal 中的某些记录在 StatusID 中有 NULL/空白值。如果评估员使用StatusId = NULL 进行评估，最终结果将返回 0。

评估

[AppraisalId] [AppraiserId] [StatusId]
1           11111           1
2           11111           2
3           11111           NULL
4           22222           4
5           22222           NULL
...

评估状态

[AppraisalStatusId] [AppraisalStatusName]
2                   Assigned
3                   Accepted
6                   Conditionally Declined
7                   Completed
10                  On Hold
11                  Order Not Accepted

鉴定人

[AppraiserId]
11111
22222

查询：

SELECT 
    AppraisalStatus.AppraisalStatusId, 
    COUNT(ISNULL(Appraisal.StatusId, 0)) AS "number_of_orders"
FROM
    AppraisalStatus
LEFT JOIN 
    Appraisal ON AppraisalStatus.AppraisalStatusId = Appraisal.StatusId
WHERE 
    AppraiserId = :AppraiserId

JSON 格式的结果

[{
  "AppraisalStatusId": 2,
  "number_of_orders": 1
}, {
  "AppraisalStatusId": 3,
  "number_of_orders": 5
}, {
  "AppraisalStatusId": 7,
  "number_of_orders": 184
}, {
  "AppraisalStatusId": 10,
  "number_of_orders": 2
}]

Answer 1

这是你想要的吗？

SELECT aps.AppraisalStatusId, COUNT(a.StatusId) as number_of_orders
FROM AppraisalStatus aps LEFT JOIN
     Appraisal a
     ON aps.AppraisalStatusId = a.StatusId AND
        a.AppraiserId = :AppraiserId
GROUP BY aps.AppraisalStatusId;

这将为给定评估员的每个状态返回一行。如果没有匹配的记录，则值为 0。

Answer 2

您可以使用SUM 代替COUNT 和GROUP BY。

SELECT 
    AppraisalStatus.AppraisalStatusId, 
    SUM(IIF(Appraisal.StatusId IS NULL, 0, 1)) AS "number_of_orders"
FROM
    AppraisalStatus
LEFT JOIN 
    Appraisal ON AppraisalStatus.AppraisalStatusId = Appraisal.StatusId
WHERE 
    AppraiserId = :AppraiserId
GROUP BY AppraisalStatus.AppraisalStatusId