Question

我一直在寻找这个，我总是得到改变做事方式的答案，但是没有解决一般性问题，即：在嵌套的SELECT中引用主查询变量。

我需要它作为嵌套查询，因为数据结构非常复杂。让我们看看我需要做的例子：

SET @teamg_id := 0;
SELECT 
    @teamg_id := player.team_id,
    player.team_id AS player_team, 
    event.local_team_id AS local_team, 
    event.visitor_team_id AS visitor_team, 
    action.unique_id AS action_id, 
    action.player_id AS player_id,
    player.name AS player_name,
    playerindex.rank AS player_pos, 
    playerindex.ses_var_nest AS ses_var_nest 
FROM  
    er_players player, 
    er_events event, 
    er_actions action 
LEFT JOIN 
    (SELECT 
        unique_id, team_id, @pn:=@pn+1 AS rank, @teamg_id AS ses_var_nest  
    FROM 
        er_players, (SELECT @pn:=-1) p2 
    WHERE 
        team_id = @teamg_id 
    ORDER BY 
        dorsal ASC, id DESC) playerindex 
ON 
    playerindex.unique_id = action.player_id 
WHERE 
    action.unique_id = '1374572622'  
    AND player.unique_id = action.player_id 
    AND event.unique_id = (SELECT event_id 
        FROM er_analysis 
        WHERE unique_id = action.analysis_id)

正如你所看到的，我需要在他的团队中返回此玩家的“索引”，按照返回的顺序返回查询（等级值），但我需要将其计算为与团队相关，而不是整个玩家表。

为了做到这一点，我需要在嵌套的SELECT中引用主查询值“player.team_id” - 我尝试过但无法做到，所以我结束了使用会话变量。

我从这个查询得到的是@teamg_id将值很好地存储在主查询中，但是当传递给嵌套查询时，它的值变为NULL：

@teamg_id  |  player_team  |  local_team  |  visitor_team  |  action_id   | player_id  |  player_name  |  player_pos  |  ses_var_nest

1374570040 |   1374570040  |  1374570040  |  1374571827    |  1374572622  | 1374570146 |   Player name |     NULL     |     NULL

我的问题是如何在嵌套查询中使用会话变量（我认为应该使用它），或者如何在其中引用主查询值。

感谢您的帮助！

编辑：这是er_players表的结构，这是给我问题的那个。如果我说“给我'玩家3'的索引”它应该给我2（0， 1,2），因为这是他队伍中的第三位球员。

+------------+------------+----------+----------+--------+
| unique_id  |  team_id   |   name   | position | dorsal |
+------------+------------+----------+----------+--------+
| 1374570066 | 1374570040 | Player 1 | Defense  |      1 |
| 1374570034 | 1374570040 | Player 2 | Defense  |      2 |
| 1374677119 | 1374571827 | Player 7 | Position |      7 |
| 1374570146 | 1374570040 | Player 3 | Attack   |      5 |
+------------+------------+----------+----------+--------+

编辑2（解决方案）：感谢Kordirko的回答和一些游戏，找到了解决方案。

 SELECT 
        player.team_id AS player_team, 
        event.local_team_id AS local_team, 
        event.visitor_team_id AS visitor_team, 
        action.unique_id AS action_id, 
        action.player_id AS player_id,
        player.name AS player_name,
        playerindex.rank AS player_pos, 
        playerindex.ses_var_nest AS ses_var_nest 
    FROM  
        er_actions action 
    LEFT JOIN er_events event 
        ON event.unique_id = (SELECT event_id FROM er_analysis WHERE unique_id = action.analysis_id) 
    LEFT JOIN er_players player 
        ON player.unique_id = action.player_id 
    LEFT JOIN 
        (SELECT 
            unique_id, team_id, team_id AS ses_var_nest ,
            case when team_id <> @lastteam
                then  (@pn:=-1)
            end AS hander, 
            case when team_id <> @lastteam
                then(@lastteam:=team_id) 
            end AS team_id_new, 
            @pn:=@pn+1 AS rank 
        FROM 
            er_players, (SELECT (@pn:=-1),(@lastteam:=0)) p2 
        ORDER BY 
            team_id, dorsal ASC, id DESC) playerindex 
    ON 
        playerindex.unique_id = action.player_id  
        AND playerindex.team_id = player.team_id   /* new join condition */     
    WHERE 
        action.unique_id = '1374572622'

在CASES之后选择@rank使其不是0两次，并在选择之前重置@rank。否则，它会变成0但进入每个队伍的第二个球员。

希望有人能找到有用的问题。

再次感谢Kordirko的时间和答案。

Answer 1

这不起作用。
SELECT子句总是在执行链的末尾进行评估，
@teamg_id变量在嵌套子查询中始终为0。

尝试这个查询，它没有经过测试（我无法看到你的数据，播放的样本数据总是有帮助的），但可能会给出预期的结果。
我注释掉了一些部分并添加了一个连接条件。

  /*  SET @teamg_id := 0; */
    SELECT 
        /* @teamg_id := player.team_id, */
        player.team_id AS player_team, 
        event.local_team_id AS local_team, 
        event.visitor_team_id AS visitor_team, 
        action.unique_id AS action_id, 
        action.player_id AS player_id,
        player.name AS player_name,
        playerindex.rank AS player_pos, 
        playerindex.ses_var_nest AS ses_var_nest 
    FROM  
        er_players player, 
        er_events event, 
        er_actions action 
    LEFT JOIN 
        (SELECT 
            unique_id, team_id, @pn:=@pn+1 AS rank, team_id AS ses_var_nest ,
            case when team_id <> @lastteam
                 then  (@pn:=-1) <> (@lastteam:=team_id) end
        FROM 
            er_players, (SELECT (@pn:=-1),(@lastteam:=0)) p2 
     /*   WHERE 
            team_id = @teamg_id */
        ORDER BY 
            team_id, dorsal ASC, id DESC) playerindex 
    ON 
        playerindex.unique_id = action.player_id  
        AND playerindex.team_id = player.team_id /* new join condition */     
    WHERE 
        action.unique_id = '1374572622'  
        AND player.unique_id = action.player_id 
        AND event.unique_id = (SELECT event_id 
            FROM er_analysis 
            WHERE unique_id = action.analysis_id)

MySQL - 嵌套选择中的引用主查询（需要嵌套）

1 个答案: