這個查詢是如何在mysql中完成的？

Question

考慮下面的表...

ID USER NUM 
1  1 69 
2  2 75 
3  3 7 
4  1 31 
5  2 18 
6  3 70 
7  1 12 
8  2 23 
9  3 42 

...這查詢將返回與最低 NUM爲每個用戶行？

結果應該像...

ID USER NUM 
7  1 12 
5  2 18 
3  3 7 

不能滿腦子都在這一個！假設它有一個GROUP BY，但我嘗試失敗的一切...任何指針？

Answer 1

SELECT t.* 
FROM tablename t 
INNER JOIN (SELECT user, MIN(num) num 
FROM tablename 
GROUP BY user) x ON t.user = x.user AND t.num = x.num 

或

SELECT t1.* 
FROM tablename t1 
LEFT JOIN tablename t2 ON t1.user = t2.user AND t1.num > t2.num 
WHERE t2.id IS NULL 

Answer 2

SELECT ID , MIN(NUM) as MIN_NUM , USER FROM usertable GROUP BY USER 

看一看演示http://sqlfiddle.com/#!2/ce2fd/1

Answer 3

這裏是另一種方法。 WITH THE正確REREFERENCE

• SQLFIDDLE

查詢而更新

select b.id, a.user, a.minnum from 
mytable as b 
join 
(select user, min(num) as minnum 
from mytable 
group by user 
) as a 
on b.user = a.user 
where b.num = a.minnum 
order by a.minnum asc 
limit 3 
; 

結果：

ID USER MINNUM 
3 3 7 
7 1 12 
5 2 18