Question

我有这个查询：

SELECT 
category,
description
FROM `players` 
INNER JOIN orders ON orders.id_player = players.player
GROUP BY id_p

这是结果：

category           description
1                  tv
1                  radio
1                  computer
2                  hamburger

我想要得到这样的东西：

category        description
1                 tv
-                 radio
-                 computer
2                 hamburger

如何更改查询？谢谢

*进行数据库更改

Answer 1

将ROW_NUMBER()与CASE结合使用可以达到预期的结果：

SELECT (CASE WHEN ROW_NUMBER() OVER 
        (PARTITION BY order_player ORDER BY (SELECT NULL)) = 1 
       THEN order_player ELSE '-' END
       ) AS order_player,
    description
FROM `players` 
INNER JOIN orders ON orders.id_player = players.player
GROUP BY id_p

Answer 2

5.5

使用此模式：

实时测试：https://www.db-fiddle.com/f/dicEcARLUJpYLcWTULsb4n/0

select category, description
from 
(
  select
      case when t.category <> @category then 
          t.category
      else
          '-'
      end as category,
      description,
      @category := category
  from tbl t cross join (select @category := '') x
  order by t.category, description
) y

输出：

|    category | description |
|-------------|-------------|
| electronics |    computer |
|           - |       radio |
|           - |          tv |
|        food |   hamburger |

使用左联接和分组依据重命名来自查询的重复结果

2 个答案: