MySQL - GROUP BY返回nil的COUNT COUNT

Question

我试图按照此示例：MySQL - ranking by count() and GROUP BY但我的rank列一直返回nil。

这里是我的查询：

SELECT 
    @rownum := @rownum+1 AS rank, 
    q.id, 
    q.Name, 
    q.count 
FROM 
(SELECT 
    Accounts.id, 
    Accounts.Name, 
    COUNT(Accounts.Name) AS count 
FROM 
    player_to_team_histories 
     INNER JOIN 
    team_histories ON team_histories.id = player_to_team_histories.team_history_id 
     INNER JOIN 
    teams ON teams.id = team_histories.team_id 
     INNER JOIN 
    accounts ON accounts.id = teams.account_id 
WHERE 
    accounts.AccountTypeId = 1 AND player_id IN (SELECT 
     player_id 
    FROM 
     player_to_team_histories 
    WHERE 
     player_to_team_histories.not_valid IS NULL AND team_history_id = (SELECT 
      team_history_id 
     FROM 
      player_to_team_histories 
       INNER JOIN 
      team_histories ON team_histories.id = player_to_team_histories.team_history_id 
     WHERE 
      player_to_team_histories.id = 574651)) 
GROUP BY Accounts.Name 
ORDER BY count DESC)q 

除了rank每列返回预期，并且rank正在恢复null的每一行。

Answer 1

你必须开始增加它之前，你的rownum初始化为0，或者通过

SET @rownum := 0; 

查询之前，或单独SELECT条款后，你的第一个FROM：

SELECT ... 
FROM 
(SELECT @rownum := 0) counter, 
(SELECT 
...)