Tsql 根据多个表中的最大（日期）科目选择记录

我有两张表：一张用于初步评估，一张用于重新评估。格式如下：

初始评估

：

• assessmentId

• personId

• 评估日期

• totalScore

重新评估

：

• assessmentId

• personId

• 评估日期

• totalScore

每个表每人包含一条记录。重新评估表中可能不包含最近的评估。因此，我需要在两个表之间选择最新的评估以及给定人员的相应总分。我尝试了以下查询，但得到了多行：

 SELECT personId, MAX(assessmentDate) AS maxSubmittedDt, TotalScore
 FROM (
    SELECT personId, assessmentDate, TotalScore
    FROM  initialAssessment
    WHERE personId = 1
    UNION
    SELECT personId, assessmentDate, TotalScore
    FROM Reassessments
    WHERE personId = 1) AS u
 Group BY personId, TotalScore
 Order By personId

---

我的问题是，如何在初始评估和重新评估表之间选择最近的评估及其相应的分数？如果重要的话，我使用的是SQl server 2005。

我注意到您的SQl没有应用从嵌套联合创建的别名“u”。此外，您的主要选择没有应用下面的组中正在应用的personId。请尝试以下操作：

SELECT u.personId AS offenderCD, MAX(u.assessmentDate) AS maxSubmittedDt, u.TotalScore
FROM (
SELECT personId, assessmentDate, TotalScore
FROM  initialAssessment
WHERE personId = 1

UNION

SELECT personId, assessmentDate, TotalScore
FROM Reassessments
WHERE personId = 1) AS u
Group BY u.personId, u.assessmentDate, u.TotalScore
Order By u.personId

会是这样的

---

如果您只想查询一个人，您可以使用TOP（n）+ORDER BY：

SELECT TOP (1) personId, assessmentDate, TotalScore
FROM (
    SELECT personId, assessmentDate, TotalScore
    FROM  initialAssessment
    WHERE personId = 1
    UNION
    SELECT personId, assessmentDate, TotalScore
    FROM Reassessments
    WHERE personId = 1) AS u
) s
ORDER BY assessmentDate DESC
;

---

但是，无论您希望在一个查询中得到多少人的结果，该选项都适用。

您不能先分组，然后在选择列表中的某些列上应用聚合函数

SELECT TOP (1) personId, assessmentDate, TotalScore
FROM (
    SELECT personId, assessmentDate, TotalScore
    FROM  initialAssessment
    WHERE personId = 1
    UNION
    SELECT personId, assessmentDate, TotalScore
    FROM Reassessments
    WHERE personId = 1) AS u
) s
ORDER BY assessmentDate DESC
;