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[英]MySQL - select row by user_id based on column value of other rows with the same user_id
[英]How to select 10 random rows(records) for each user_id column value in SQL?
我有一個數據庫,希望為每個User_ID
選擇10個隨機行。
到目前為止,我已經有了這段代碼,但不確定如何為每個User_ID
值選擇10個隨機行。
SELECT User_ID
FROM Database
ORDER BY RAND()
LIMIT 10
GROUP BY User_ID
在8.0之前的MySQL中,這很痛苦。 這是一種方法:
select d.*
from (select d.*,
(@rn := if(@u = user_id, @rn + 1,
if(@u := user_id, 1, 1)
)
) as rn
from (select d.* from database d order by user_id, rand()
) d cross join
(select @u := 0, @rn := 0) params
) d
where rn <= 10;
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