我建议使用cte删除：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY id, CONVERT(date, ts_col) ORDER BY ts_col) rn
    FROM yourTable
)

DELETE
FROM cte
WHERE rn > 1;     -- targets all records per day except for the first one

如果只有两列，请使用聚合：

select id, cmin(timestamp) as timestamp
from t
group by id, convert(date, timestamp);

如果您有许多列并且想要完整的行，那么 row_number() 可能是最好的选择：

select t.*
from (select t.*,
             row_number() over (partition by id, convert(date, timestamp) order by timestamp) as seqnum
      from t
     ) t
where seqnum = 1;

您可以使用此选择来控制：

select  a.* from yourtable a
inner join
(
    select id,convert(date,[datetime]) [date], MIN([datetime]) [datetime]
    from yourtable
    group by id,convert(date,[datetime])
) b on a.id = b.id and convert(date,a.[datetime]) = b.[date] and a.[datetime] <> b.[datetime]

然后删除：

delete  a from yourtable a
inner join
(
    select id,convert(date,[datetime]) [date], MIN([datetime]) [datetime]
    from yourtable
    group by id,convert(date,[datetime])
) b on a.id = b.id and convert(date,a.[datetime]) = b.[date] and a.[datetime] <> b.[datetime]