Question

运行以下查询

SET @rownum := 0;    
SELECT customer_id, @rownum := @rownum +1 AS rank, score
FROM game_table_customers gtc
INNER JOIN customers c ON c.customers_id = gtc.customer_id
INNER JOIN game_table gt ON gtc.table_id = gt.table_id
WHERE c.my_team =11095
AND gt.event_id =21110
ORDER BY score DESC
LIMIT 0 , 30

正确的结果应如下所示

CustID  Rank    Score
2        1     130000
39       2     99426
84       3     99178
259      4     98963
339      5     97796

但是，我得到的是以下

CustID  Rank    Score
2        2      130000
39      11      99426
84      20      99178
259     54      98963
339     69  97796

当我排除event_id子句时，我得到了正确的结果。但是当包含event_id时，它会扭曲它。我只尝试了event_id（删除my_team子句）和相同的错误结果。

非常感谢任何关于结果可能会被取消的想法/建议

Answer 1

我想这与在每种情况下选择的执行计划以及应用行号的混合有关 - 在某些计划中。计算行号，然后评估WHERE条件，因此您可以看到非连续的行号。

试试这个（首先得到你需要的30个结果，然后应用行号）：

SET @rownum := 0; 
SELECT customer_id, @rownum := @rownum +1 AS rank, score
FROM
  ( SELECT customer_id, score
    FROM game_table_customers gtc
      INNER JOIN customers c ON c.customers_id = gtc.customer_id
      INNER JOIN game_table gt ON gtc.table_id = gt.table_id
    WHERE c.my_team =11095
      AND gt.event_id =21110
    ORDER BY score DESC
    LIMIT 0 , 30
  ) tmp
ORDER BY score DESC

我现在无法测试，但您也可以尝试：

SELECT customer_id, @rownum := @rownum +1 AS rank, score
FROM game_table_customers gtc
  INNER JOIN customers c ON c.customers_id = gtc.customer_id
  INNER JOIN game_table gt ON gtc.table_id = gt.table_id
  CROSS JOIN (SELECT @rownum := 0 AS rn) dummy  
WHERE c.my_team =11095
  AND gt.event_id =21110
ORDER BY score DESC
LIMIT 0 , 30

MySQL变量没有正确递增

1 个答案: