SQL - 行数を維持しながら、繰り返される行を null 値に置き換える

これを行うには、1 年以内に行を列挙します。次に、最初の 1 つを除くすべてを更新します。

with toupdate as (
      select t.*, row_number() over (partition by [year] order by [date]) as seqnum
      from t
     )
update toupdate
    set [year] = NULL
    where seqnum > 1;

これを select にしたい場合 ステートメント:

with ts as (
      select t.*, row_number() over (partition by [year] order by [date]) as seqnum
      from t
     )
select [date],
       (case when seqnum = 1 then [year] end) as [year]
from ts;