这意味着 Question_id 6
与 Question_id 10
相似度为 84%。
Question_id 6
的类似问题共有 12 个。
我只是最相关的问题,或者前 7 个相关问题。
我见过Mysql delete order by 并尝试过:
DELETE FROM exam_relatedquestion
WHERE
`exam_relatedquestion`.id IN (
SELECT
`exam_relatedquestion`.id
FROM
(
SELECT `exam_relatedquestion`.id
FROM `exam_relatedquestion`
GROUP BY
`exam_relatedquestion`.from_question_id_id
ORDER BY
`exam_relatedquestion`.similarity DESC
LIMIT 7
) a
)
但是错误信息是:
[Err] 1055 - Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'den.exam_relatedquestion.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
如何删除与问题不相关的前 7 行?
最佳答案
那是行不通的。无论如何,您的伪代码都不正确,因为排序方向错误。
无论如何,您都可以使用变量来枚举问题,然后使用join
:
delete erq
from exam_relatedquestion erq join
(select erq2.*,
(@rn := if(@q = erq2.from_question_id_id, @rn + 1,
if(@q := erq2.from_question_id_id, 1, 1)
)
) as seqnum
from exam_relatedquestion erq2 cross join
(select @rn := 0, @q := -1) params
order by erq2.from_question_id_id, score desc
) erq2
on erq2.id = erq.id
where rn > 7;
关于MySQL 删除行 ORDER BY COUNT DESC,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44014179/