针对分组记录获取值为 true 的单行 mysql

Question

我的样本数据：

id     role_id    permission_id      access_granted      user_id
------------------------------------------------------------------
1         1            10                  1               115
------------------------------------------------------------------
2         1            5                   1               115   
------------------------------------------------------------------
3         2            10                  0               115
------------------------------------------------------------------
4         2            8                   0               115
------------------------------------------------------------------

使用permission_id进行分组，对于重复的permission_id，结果应该具有值为true的行。正如我们所看到的，查询是按permission_id分组的，并且为permission_id 10选择了值为true的行，而对于其他行，权限id不会重复，因此值false被按原样选择。

预期结果：

id     role_id    permission_id      access_granted      user_id
------------------------------------------------------------------
1         1            10                  1               115
------------------------------------------------------------------
2         1            5                   1               115   
------------------------------------------------------------------
4         2            8                   0               115
------------------------------------------------------------------

下面是我尝试获取上述结果的查询。

select id, role_id, permission_id,
case when max(access_granted) = true then true else false end as access_granted,
user_id as user_id  
from temp_permission group by permission_id;

需要优化且真实的查询，在任何情况下都不会失败。

创建表查询

CREATE TABLE temp_permission (
    id int auto_increment primary key,
    role_id int,
    permission_id int,
    access_granted tinyInt(1),
    user_id int
);

根据屏幕截图对表进行虚拟数据查询

INSERT INTO `temp_permission` (`id`, `role_id`, `permission_id`, `access_granted`, `user_id`) VALUES ('1', '1', '10', '1', '115');
INSERT INTO `temp_permission` (`id`, `role_id`, `permission_id`, `access_granted`, `user_id`) VALUES ('2', '1', '5', '1', '115');
INSERT INTO `temp_permission` (`id`, `role_id`, `permission_id`, `access_granted`, `user_id`) VALUES ('3', '2', '10', '0', '115');
INSERT INTO `temp_permission` (`id`, `role_id`, `permission_id`, `access_granted`, `user_id`) VALUES ('4', '2', '8', '0', '115');

如果您无法将数据插入 access_granted 列，请替换

1 = b'1' & 0 = b'0'

Answer 1

您可以简单地根据

permission_id

和

access_granted

按降序排列行，然后根据

permission_id

选择不同的行。比如：

WITH ordered_rows AS (
  SELECT id, role_id, permission_id, access_granted, user_id,
         ROW_NUMBER() OVER (PARTITION BY permission_id ORDER BY access_granted DESC) as row_num
  FROM temp_permission
)
SELECT id, role_id, permission_id, access_granted, user_id
FROM ordered_rows
WHERE row_num = 1;

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