帮助 SQL 2005 和内部联接答案

【问题标题】：Help with SQL 2005 and inner join帮助 SQL 2005 和内部联接
【发布时间】：2009-12-18 15:57:22
【问题描述】：

我正在尝试内部连接 2 个临时表
我知道这可以做到，我以前做过，但我完全忘记了如何做到这一点

请告诉我
以下是我尝试执行的查询

select tmp1.*, tmp2.cnt from
(
    select 
        1 as ClassificationType,
        tblMatches.IdGame,
        tblMatches.IdPlayer,
        sum(Score) as Score, sum(Points) as Points, sum(OpponentScore) as OpponentScore,
        count(ID) as MatchesCount, count(distinct IdCompetition) as CompetitionsCount
    from 
        tblMatches  
    group by IdPlayer, IdGame   
) as tmp1
inner join (select IdWinner, count(IdWinner) as cnt from tblCompetitions where IdWinner = tmp1.IdPlayer) as tmp2 
            on tmp2.IdWinner = tmp1.IdPlayer

这将失败
我想我不允许在创建 tmp2 的子查询中使用 tmp1

消息 4104，第 16 级，状态 1，第 17 行多部分标识符无法绑定“tmp1.IdPlayer”。

【问题讨论】：

标签： sql-server inner-join

【解决方案1】：

您不是要连接两个临时表，而是要连接两个派生表。

除非在 SELECT 子句中，否则您无法访问其外部的一个派生表的内部数据。

尝试以下方法：

select tmp1.*, tmp2.cnt from
(
    select 
        1 as ClassificationType,
        tblMatches.IdGame,
        tblMatches.IdPlayer,
        sum(Score) as Score, sum(Points) as Points, sum(OpponentScore) as OpponentScore,
        count(ID) as MatchesCount, count(distinct IdCompetition) as CompetitionsCount
    from 
        tblMatches      
    group by IdPlayer, IdGame   
) as tmp1
inner join (select IdWinner, count(IdWinner) as cnt from tblCompetitions GROUP BY IdWinner) as tmp2 
                on tmp2.IdWinner = tmp1.IdPlayer

【讨论】：

【解决方案2】：

select
    1 as ClassificationType,
    tmp1.IdGame,
    tmp1.IdPlayer,
    sum(tmp1.Score) as Score,
    sum(tmp1.Points) as Points,
    sum(tmp1.OpponentScore) as OpponentScore,
    count(tmp1.ID) as MatchesCount,
    count(distinct tmp1.IdCompetition) as CompetitionsCount,
    count(tmp2.IdWinner) as cnt
from 
    tblMatches tmp1
    inner join
    tblCompetitions tmp2
        on tmp2.IdWinner = tmp1.IdPlayer
group by
    tmp1.IdPlayer,
    tmp1.IdGame

【讨论】：

【解决方案3】：

tmp2 中的 where 子句重复了连接条件：

inner join (select IdWinner, count(IdWinner) as cnt 
            from tblCompetitions 
            where IdWinner = tmp1.IdPlayer) as tmp2 
on         tmp2.IdWinner = tmp1.IdPlayer

只需删除where 子句。此外，就像 Astander 在他现已删除的帖子中指出的那样，第二个查询也需要 group by：

inner join (select IdWinner, count(IdWinner) as cnt 
            from tblCompetitions
            group by IdWinner) as tmp2 
on         tmp2.IdWinner = tmp1.IdPlayer

您不能从子查询中引用外部查询的原因是，这会使联接的右侧部分依赖于联接的左侧部分。

【讨论】：

【解决方案4】：

您实际上不应该需要第二个子查询。这个呢？

SELECT tmp1.ClassificationType, tmp1.IdGame, tmp1.IdPlayer,
       COUNT(tblCompletions.IdWinner) as cnt FROM
(
    SELECT 
        1 as ClassificationType,
        tblMatches.IdGame,
        tblMatches.IdPlayer,
        sum(Score) as Score, sum(Points) as Points, sum(OpponentScore) as OpponentScore,
        count(ID) as MatchesCount, count(distinct IdCompetition) as CompetitionsCount
    FROM 
        tblMatches      
    GROUP BY IdPlayer, IdGame   
) as tmp1
INNER JOIN tblCompletions ON tmp1.IdPlayer = tblCompletions.IdWinner
GROUP BY tmp1.ClassificationType, tmp1.IdGame, tmp1.IdPlayer

【讨论】：