Question

我有一个查询，我想通过输入的最新日期和描述ID获得不同的描述。我可以得到一个明显的部分，但我遇到麻烦，试图获取ID，因为我在日期使用MAX。这是查询：

SELECT DISTINCT Resource.Description, MAX(arq.DateReferred) AS DateReferred, arq.AssessmentResourceID
FROM AssessmentXResource AS arq 
INNER JOIN Resource ON arq.ResourceID = Resource.ResourceID 
INNER JOIN Assessment AS aq 
INNER JOIN [Case] AS cq ON aq.CaseID = cq.CaseID 
INNER JOIN [Plan] AS pq ON cq.CaseID = pq.CaseID ON arq.AssessmentID = aq.AssessmentID
WHERE     (pq.PlanID = 22)
GROUP BY Resource.Description, arq.AssessmentResourceID
ORDER BY Resource.Description

我确定它很简单，但我没有看到它。

Answer 1

SELECT
    Resource.Description,
    arq.DateReferred AS DateReferred,
    arq.AssessmentResourceID
FROM
    Resource
INNER JOIN
    AssessmentXResource AS arq 
        ON arq.ResourceID = Resource.ResourceID 
        AND arq.DateReferred = (
                                SELECT
                                    MAX(DateReferred)
                                FROM
                                    AssessmentXResource
                                WHERE
                                    ResourceID = Resource.ResourceID
                               )
INNER JOIN
    Assessment AS aq
        ON arq.AssessmentID = aq.AssessmentID
INNER JOIN
    [Case] AS cq
        ON aq.CaseID = cq.CaseID 
INNER JOIN
    [Plan] AS pq
        ON cq.CaseID = pq.CaseID
WHERE
    (pq.PlanID = 22)
ORDER BY
    Resource.Description

Answer 2

我没有看到加入[案例]表的原因，所以我把它留了出来。如果您出于某种原因需要，可以将其添加回来。

SELECT
     RES.Description,
     ARQ.DateReferred,
     ARQ.AssessmentResourceID
FROM
     AssessmentXResource ARQ
INNER JOIN Resource ON
     ARQ.ResourceID = RES.ResourceID
INNER JOIN Assessment AQ ON
     AQ.AssessmentID = ARQ.AssessmentID
INNER JOIN [Plan] PQ ON
     PQ.CaseID = AQ.CaseID
LEFT OUTER JOIN AssessmentXResource ARQ2 ON
     ARQ2.ResourceID = ARQ.ResourceID AND
     ARQ2.DateReferred > ARQ.DateReferred
WHERE
     PQ.PlanID = 22 AND
     ARQ2.ResourceID IS NULL

如果数据中的相同ResourceID存在相同的DateReferred值，则可能无法实现。您应该针对该情况提出业务规则，并为其适当更改查询。此外，如果不能保证您的AssessmentXResource行的评估，计划和案例表中有匹配的行，这将与您的查询略有不同。您可以通过为ARQ2添加联接来使其工作，但这会影响性能，也会更复杂一些。如果你需要，然后发表评论，我可以改变查询来处理它，或者你可以自己解决。

Answer 3

简短回答：如果按ID分组，则max函数不起作用。您将最终返回每个不同ID的Max值。即一切

您可能需要更改子查询表示，但您明白了。

从表中选择id，val 其中val =（从表中选择max（val））

使用日期字段获取不同的记录？

3 个答案: