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3つの異なるテーブルの最大日付レコードを取得するこのクエリがあります。これらのテーブルを結合して、すべてのテーブルにそれぞれの日付を一緒に返すようにすることができます。ただし、返されるこれら3つのレコードの最大値を選択する方法を見つけるのに問題があります。何か案は？

SELECT MAX (Date_submitted ) as a
FROM [AngelSQL] . [dbo]. [LSN_RESPONSES] , ACCOUNTS , LSN_ENTRIES , GB3_ASSOCIATIONS
where
LSN_RESPONSES . USER_ID = accounts . username
and LoginName = 'admin'
and TakenFromCourseId = 'TT-TC-TS-TD-Test-Test'
and LSN_RESPONSES . PARENT_ID = LSN_ENTRIES .ENTRY_ID
and LSN_RESPONSES . PARENT_ID = GB3_ASSOCIATIONS .LSN_ENTRY_ID
union
SELECT MAX ( dateEnd ) as a
FROM [AngelSQL] . [dbo]. [qti_assessment_attempt] ,dbo . ACCOUNTS, COURSES, qti_question_containers, GB3_ASSOCIATIONS
where   accounts . PERSON_ID = qti_assessment_attempt .person_id
and
taken_from_course_container_id = courses. CONTAINER_ID
and
accounts .LoginName = 'admin'
and COURSES . COURSE_ID= 'TT-TC-TS-TD-Test-Test'
and qti_assessment_attempt . question_container_id = qti_question_containers. id
and qti_question_containers . entry_ID = GB3_ASSOCIATIONS .LSN_ENTRY_ID
union
SELECT MAX ( PostDate ) as a
FROM dbo . ACCOUNTS, DiscussionPost , DiscussionForum , GB3_ASSOCIATIONS
where
accounts .USERNAME = DiscussionPost. AuthorId
and
LoginName ='admin'
and
discussionpost . CourseContext = 'TT-TC-TS-TD-Test-Test'
and
DiscussionPost . ForumId = DiscussionForum .ForumId
and DiscussionForum . EntryId = GB3_ASSOCIATIONS .LSN_ENTRY_ID}
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1 に答える 1

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次のように、クエリをサブクエリ/CTE として使用します。

with t as (<put your query here>)
select max(a)
from t
于 2012-07-27T19:12:54.010 に答える