为什么我的SQL查询将结果加倍

Question

我试图在两个表之间进行连接。完成后的查询如下：

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 

在M表让我一个表，这个结构（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 

的OrgCountry表确实具有这样的结构体（I只写有意义行让你明白，明明1996年和1984年之间有其他条目，但在这个例子中我把它剪）：

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 

如果我让喜欢他们之间的连接以上，我得到的结果如下：

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？我想要的只是汇总为国家和得到：

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，由于亚特兰大和洛杉矶是美国的城市，所以第一排会更改。

Answer 1

查询的核心如下。您sqlfiddle是不是足够的代表性问题，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;