如何查询从 table 中删除相同的数据？

Question

我想删除它以使输出看起来像这样。在一组中应该只有 1 user_id.

select distinct group_id, user_id, count(*)
from pin_users
where group_id in (select group_id from pin_users)
group by group_id, user_id
having count(*) > 1

我得到了所有 user_id、group_id 并计数超过 1，但我不知道如何删除重复项，只剩下 1。

Ps。我的英语可能不完美，如有错误请原谅

Answer 1

如果是sql-server，试试这个：

-- mockup data
declare @Raw table (
    id nvarchar(max),
    group_id nvarchar(max),
    user_id nvarchar(max)
                   )

insert into @Raw values ('p001', 'aaa', 'ava001'), ('p002', 'aaa', 'ava001'), ('p003', 'bbb', 'ava001'), ('p004', 'bbb', 'ava001');

-- check this query
with A as (
    select id, ROW_NUMBER() over(partition by group_id, user_id order by id) as RN 
from @Raw)
delete from @Raw where id in (select id from A where A.RN > 1)

-- verify table
select * from @Raw

Answer 2

例如，sql服务器应该是这样的

delete u1
from pin_users u1
 join (
   select min(id) id, group_id, user_id
   from pin_users
   group by group_id, user_id
   ) u2
   on u1.group_id = u2.group_id
  and u1.user_id = u2.user_id
  and u1.id <> u2.id

Answer 3

进行子查询以获取用户和组的任意组合的最小 ID 列表。然后删除所有其他内容。

DELETE FROM pin_users WHERE id NOT IN (
    SELECT min(id) as id
    FROM pin_users
    GROUP BY group_id, user_id
)

如何查询从 table 中删除相同的数据？

How to query for delete the same data out of the table?

sql