用一组特定值标记的所有行 [英] All rows tagged with a specific set of values

问题描述

更具体地说，对于作为 sql server 表(包括帮助表 QuestionsWithTags)的 Questions 和 Tags 之间的多对多关系，需要一个查询/sp 返回具有以下标记集t1"的所有问题、t2"和t3".那里的鉴别器不是任何标签，而是所有标签，不多也不少.

To be more specific, for a many to many relation between Questions and Tags as sql server tables (including the helper table QuestionsWithTags), is needed a query/sp that returns all the questions that have the following tag set "t1", "t2" and "t3". The discriminator there is not any of the tags, but all of them, no less, no more than that.

提前致谢.

推荐答案

您可以使用聚合和 sharing 子句来解决这个问题:

You can solve this using aggregation and a having clause:

select questionid
from QuestionsWithTags qwt
group by questionid
having count(distinct tag) = 3 and
       count(distinct case when tag in ('t1', 't2', 't3') then tag end) = 3;

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