Question

我正在尝试在两个表之间建立连接。完成的查询如下：

select 
    cast(M.Rank as signed) as Rank,
    O.Country,
    O.Continent,
    M.Gold, 
    M.Silver, 
    M.Bronze, 
    M.Total
from

(
select @rownum := @rownum + 1 as RankStd,
    CASE
        WHEN (@Gold=T.Gold and @Silver=T.Silver and @Bronze=T.Bronze) 
        THEN @rank := @rank 
        ELSE @rank := @rownum 
    END as Rank,



        (@Gold:=T.Gold) Gold,
        (@Silver:=T.Silver) Silver,
        (@Bronze:=T.Bronze) Bronze,
        T.Total,
        T.City,
        T.Season

from

(


select 
    sum(Gold) as Gold,
    sum(Silver) as Silver,
    sum(Bronze) as Bronze,
    sum(Total) as Total,
    City,
    Season
from
(
    select 
    City,
    Season,
    case when Medal ='gold' then 1 else 0 end as Gold,
    case when Medal ='silver' then 1 else 0 end as Silver,
    case when Medal ='bronze' then 1 else 0 end as Bronze,
    1 as Total
    from MedalResults
    where Country = 'ITA'
    and Season='Summer'


) a

group by City

) T

    CROSS JOIN (SELECT @rownum := 0, 
                       @Gold := 0, 
                       @Silver := 0, 
                       @Bronze := 0, 
                       @rank := 1) v

    order by Gold desc, Silver DESC, Bronze DESC

)M

join OrgCountry O
on O.City = M.City and O.Season=M.Season

order by Rank

M表为我提供了一个具有这种结构的表（我只写第一行）：

RankStd Rank Gold Silver Bronze Total   City        Season
-----------------------------------------------------------
1       1    26   18     24     68    Los Angeles   Summer
2       2    19   23     21     63    London        Summer
3       3    17   17     14     48    Athina        Summer
4       4    14   6      5      25    Antwerpen     Summer
5       5    13   10     13     36    Roma          Summer
6       6    13   10     12     35    Atlanta       Summer

OrgCountry表确实有这样的结构（我只写有意义的行让你明白，显然在1996年和1984年之间还有其他条目，但是对于这个例子我把它剪掉了）：

ID   Year   City       Country        Continent   Season
-----------------------------------------------------
1    2012   London       Great Britain  Europe      Summer
2    2008   Beijing      China          Asia        Summer
3    2004   Athina       Greece         Europe      Summer
4    2000   Sydney       Australia      Oceania     Summer
5    1996   Atlanta      United States  Americas    Summer
6    1984   Los Angeles  United States  Americas    Summer

如果我像上面那样在他们之间进行连接，我得到的结果加倍：

Rank   Country        Continent   Gold   Silver   Bronze   Total
-------------------------------------------------------------
1      United States  Americas    26     18       24       68
1      United States  Americas    26     18       24       68
2      Great Britain  Europe      19     23       21       63
2      Great Britain  Europe      19     23       21       63
2      Great Britain  Europe      19     23       21       63
3      Greece         Europe      17     17       14       48
3      Greece         Europe      17     17       14       48
3      Greece         Europe      17     17       14       48

为什么这样？我想要的只是汇总国家和获得：

Rank Gold Silver Bronze Total   Country        Season
-----------------------------------------------------------
1    39   28     36     113     United States  Summer
2    19   23     21     63      Great Britain  Summer
3    17   17     14     48      Greece         Summer
4    14   6      5      25      Netherlands    Summer
5    13   10     13     36      Italy          Summer
6    13   10     12     35      Australia      Summer

等等。请注意，第一行已更改，因为亚特兰大和洛杉矶是美国的城市。

Answer 1

您的查询的核心如下。您的sqlfiddle不能充分代表问题进一步回答：

SELECT y.country
     , x.medal
     , COUNT(*) subtotal 
  FROM medalresults x 
  JOIN (SELECT DISTINCT city, country FROM orgcountry) y 
    ON y.city = x.city 
 WHERE x.country = 'ITA' 
 GROUP 
    BY country
     , medal;

......或者可能......

SELECT y.country
     , SUM(CASE WHEN medal = 'gold' THEN 1 ELSE 0 END) gold
     , SUM(CASE WHEN medal = 'silver' THEN 1 ELSE 0 END) silver
     , SUM(CASE WHEN medal = 'bronze' THEN 1 ELSE 0 END) bronze
  FROM medalresults x 
  JOIN (SELECT DISTINCT city, country FROM orgcountry) y 
    ON y.city = x.city 
 WHERE x.country = 'ITA' 
 GROUP 
    BY country;

为什么我的SQL查询将结果加倍

1 个答案: