Question

T有下表：

mid pid   price
1   100   10
1   200   10
1   300   10
1   400   10
2   500   20
2   600   30
2   700   20
3   800   40
3   900   50

我想找到每个中间价格最低的pid。

因为我正在查询这段代码。

SELECT t1.mid,t1.pid 
FROM tableName t1
JOIN (
  SELECT mid, min(price) as min_price
  FROM tableName
  GROUP BY mid
) as t2 on t1.mid = t2.mid and t1.price = t2.min_price;

理想情况下，它应该给出结果，但在我的情况下，每组中有多个pid具有相同的价格。所以它打印了所有的结果。

但我只是想为每个中间限制1行。

有没有办法做到这一点？我有一个 sqlfiddle demo

Answer 1

select s.mid,s.pid,s.price
from
(
SELECT t1.mid,t1.pid,t1.price,
        if (t1.mid <> @p, @rn:=1,@rn:=@rn+1) rn,
        @p:=t1.mid p
FROM (select @rn:=0,@p:=0) rn,t t1 
order by t1.mid,t1.price,t1.pid
) s where s.rn = 1

Answer 2

尝试：http://www.sqlfiddle.com/#!2/e2244c/71

SELECT t1.mid, MIN(DISTINCT t1.pid) AS Expr1
FROM            tableName as t1
INNER JOIN
tableName AS tableName_1 ON t1.mid = tableName_1.mid
GROUP BY t1.mid
ORDER BY MIN(DISTINCT t1.pid) DESC

Answer 3

试试这个：

select t1.*
from tablename t1
inner join (select mid, min(pid) min_pid from
(select t1.mid,t1.pid
FROM tablename t1
inner join (select mid,
    min(price) as min_price
    FROM tablename
    GROUP BY mid) t2 on t1.mid = t2.mid
and t1.price = t2.min_price) t
group by mid) t2 on t1.mid = t2.mid
and t1.pid = t2.min_pid
;

它以最低价格和最小pid生成行。

Answer 4

它起作用：

SELECT t1.mid,t1.pid FROM tableName t1 
INNER JOIN ( 
     SELECT mid AS mid1, pid AS pid1, min(price) as min_price FROM  tableName GROUP BY mid 
) as t2
on t1.mid = t2.mid1 and t1.price = t2.min_price and t1.pid = t2.pid1;

在mysql中进行groupby时只选择一行

4 个答案: