内部加入问题

时间:2015-02-21 07:10:23

标签: mysql join inner-join

我尝试使用内部联接将3个表连接在一起,但结果显示的记录多于应该存在的记录。我的数据表设置如下:

Table:gameday.atbats

   GameName                     Inning num  b   s   o   Batter   Pitcher      Result
-----------------------------------------------------------------------------------------
    gid_2008_09_24_cinmlb_houmlb_1  1   1   2   3   1   457803  150116  Jay Bruce strikes out swinging.  
    gid_2008_09_24_cinmlb_houmlb_1  1   2   1   0   2   433898  150116  Jeff Keppinger lines out to right fielder Hunter Pence.  
    gid_2008_09_24_cinmlb_houmlb_1  1   3   3   1   2   458015  150116  Joey Votto singles on a line drive to right fielder Hunter Pence.  
    gid_2008_09_24_cinmlb_houmlb_1  1   4   2   3   3   429665  150116  Edwin Encarnacion called out on strikes.  
    gid_2008_09_24_cinmlb_houmlb_1  1   5   1   2   0   430565  459371  Kazuo Matsui singles on a line drive to right fielder Jay Bruce.  
-----------------------------------------------------------------------------------------

Table: Gameday.pitches
 GameName                   GameAtBatID      Result
------------------------------------------------------
gid_2008_09_24_cinmlb_houmlb_1  1       Called Strike
gid_2008_09_24_cinmlb_houmlb_1  1       Ball
gid_2008_09_24_cinmlb_houmlb_1  1       Swinging Strike
gid_2008_09_24_cinmlb_houmlb_1  1       Ball
gid_2008_09_24_cinmlb_houmlb_1  1       Foul
gid_2008_09_24_cinmlb_houmlb_1  1       Foul
gid_2008_09_24_cinmlb_houmlb_1  1       Swinging Strike
gid_2008_09_24_cinmlb_houmlb_1  2       Ball
gid_2008_09_24_cinmlb_houmlb_1  2       In play, out(s)
gid_2008_09_24_cinmlb_houmlb_1  3       Called Strike
gid_2008_09_24_cinmlb_houmlb_1  3       Ball
--------------------------------------------------------

Table:batters
   GameName                     id         name_display_first_last
----------------------------------------------------------------------------------
gid_2008_09_24_cinmlb_houmlb_1  407783      Geoff Geary
gid_2008_09_24_cinmlb_houmlb_1  209315      David Newhan
gid_2008_09_24_cinmlb_houmlb_1  115629      LaTroy Hawkins
gid_2008_09_24_cinmlb_houmlb_1  113889      Darin Erstad
gid_2008_09_24_cinmlb_houmlb_1  457803      Jay Bruce
gid_2008_09_24_cinmlb_houmlb_1  433898      Jeff Keppinger
gid_2008_09_24_cinmlb_houmlb_1  458015      Joey Votto
gid_2008_09_24_cinmlb_houmlb_1  429665      Edwin Encarnacion
---------------------------------------------------------------------------

我正在运行看似相当标准的内连接组,将各个表连接在一起,以获得一个输出,显示每个击球手在整个游戏中所做的一切。我的代码如下:

SELECT 


    gameday.atbats.inning,
    gameday.batters.name_display_first_last,
    gameday.pitches.Result
FROM
 gameday.atbats
        Inner join 
     gameday.pitches on gameday.atbats.num = gameday.pitches.gameAtBatID
        inner join
    gameday.batters on gameday.atbats.batter = gameday.batters.ID

    where gameday.atbats.gamename = "gid_2008_09_24_cinmlb_houmlb_1"

我的问题是,当我运行此查询时,击球手的结果比他们应该的多。例如,在第一局比赛中,杰特布鲁斯(atbats表中的数字1)在第一局中应该有7个投球,但是当我运行查询时,他将投掷10个投球。我做错了什么来得到这些结果。另外,我知道这些字段名称的名字很可怕,但是它们是由其他人命名的,我还没有机会改变它们。

2 个答案:

答案 0 :(得分:2)

我敢打赌,atbats.numpitches.GameAtBatID并不意味着全球唯一地识别击球,而是他们只能唯一地识别击球在给定游戏中 。因此,除了将atbats.GameName限制为所需游戏外,您还需要指定pitches.GameName = atbats.GameName

SELECT gameday.atbats.inning,
       gameday.batters.name_display_first_last,
       gameday.pitches.Result
  FROM gameday.atbats
  JOIN gameday.pitches
    ON gameday.atbats.GameName = gameday.pitches.GameName
   AND gameday.atbats.num = gameday.pitches.GameAtBatID
  JOIN batters
    ON gameday.atbats.GameName = gameday.batters.GameName
   AND gameday.atbats.batter = gameday.batters.ID
 WHERE gameday.atbats.gamename = 'gid_2008_09_24_cinmlb_houmlb_1'

(注意:我还为AND添加了类似的batters,因为虽然batters.ID的值足够大,但真正 似乎是合理的>一个独特的领域,包含它是有意义的。)

答案 1 :(得分:1)

这是事实,因为SQL工作从TOP到buttom所以当你加入前两个表时你会有

Inner join 
     gameday.pitches on gameday.atbats.num = gameday.pitches.gameAtBatID

您将获得这些结果

GameName                   GameAtBatID      Result         Batter    
--------------------------------------------------------------------------
gid_2008_09_24_cinmlb_houmlb_1  1       Called Strike      457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Ball               457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Swinging Strike    457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Ball               457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Foul               457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Foul               457803 
gid_2008_09_24_cinmlb_houmlb_1  1       Swinging Strike    457803 
gid_2008_09_24_cinmlb_houmlb_1  2       Ball               433898
gid_2008_09_24_cinmlb_houmlb_1  2       In play, out(s)    433898
gid_2008_09_24_cinmlb_houmlb_1  3       Called Strike      458015 
gid_2008_09_24_cinmlb_houmlb_1  3       Ball               458015 

然后当你添加

的新连接线时
inner join
    gameday.batters on gameday.atbats.batter = gameday.batters.ID

您将从三个表中获得这些结果

name_display_first_last   GameAtBatID      Result          Batter    
    --------------------------------------------------------------------------
    Jay Bruce                1       Called Strike      457803 
    Jay Bruce                1       Ball               457803 
    Jay Bruce                1       Swinging Strike    457803 
    Jay Bruce                1       Ball               457803 
    Jay Bruce                1       Foul               457803 
    Jay Bruce                1       Foul               457803 
    Jay Bruce                1       Swinging Strike    457803 
    Jeff Keppinger           2       Ball               433898
    Jeff Keppinger           2       In play, out(s)    433898
    David Newhan             3       Called Strike      458015 
    David Newhan             3       Ball               458015