MySQL数据库，选择大小写，并获取两个值而不是一个值

Question

如果我想同时了解 a_player1_name 和 b_player1_name，我该如何修改它？

现在返回第一个找到的值。我的意思是，a_player1_name 或 b_player1_name，但不是两者。两者都是必需的。

当chart_matches.a_player1_id = user_list.id时，a_player1_name应为user_list.player_name。

当chart_matches.b_player1_id = user_list.id时，b_player1_name应该是user_list.player_name。

请帮忙，谢谢。

SELECT case user_list.id
            when chart_matches.a_player1_id
            then user_list.player_name
       end AS a_player1_name

       , case user_list.id
            when chart_matches.b_player1_id
            then user_list.player_name
       end AS b_player1_name

FROM chart_matches
     , all_lists
     , user_list

WHERE chart_matches.chart_id = 106
      AND ((chart_matches.a_team_id = all_lists.id AND chart_matches.a_player1_id = user_list.id)
      OR (chart_matches.b_team_id = all_lists.id AND chart_matches.b_player1_id = user_list.id))

Answer 1

看起来您只是想聚合您的结果(请注意下面版本中的 MAX() 函数)。

您的原始记录将获得 2 条记录 - 每位玩家一条。因此，您必须将记录聚合在一起，并且对于此 MAX() 本质上保留了与特定玩家匹配的记录中的值。

SELECT max(case user_list.id
            when chart_matches.a_player1_id
            then user_list.player_name
            else null
       end) AS a_player1_name

       , max(case user_list.id
            when chart_matches.b_player1_id
            then user_list.player_name
            else null
       end) AS b_player1_name

FROM chart_matches
     , all_lists
     , user_list

WHERE chart_matches.chart_id = 106
      AND chart_matches.a_team_id = all_lists.id
      AND (chart_matches.a_player1_id = user_list.id OR chart_matches.b_player1_id = user_list.id)