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Question

我是SQL Server数据库和查询的新手。

我有一个带有DateTime和Current的SQL Server数据库表。当前可能具有NULL值。

仅当上一条或下一条记录具有某个值时，我才想用零替换Current列中的NULL值。提供的DateTime以升序排序。

请帮助我编写一个SQL查询或存储过程和SQL查询的组合。

还可以帮助我用DateTime升序对现有表进行排序。 DateTime不是正在运行的系列。

Answer 1

您可以使用可更新的CTE和窗口功能：

with toupdate as (
      select t.*, lag(current) over (order by datetime) as prev_current,
             lead(current) over (order by datetime) as next_current
      from t
     ) 
update toupdate
    set current = 0
    where current is null and (prev_current is not null or next_current is not null);

如果您只想在select查询中增加一列（而不是更改数据），则：

with t as (
      select t.*, lag(current) over (order by datetime) as prev_current,
             lead(current) over (order by datetime) as next_current
      from t
     ) 
select t.*,
       (case when current is null and (prev_current is not null or next_current is not null)
             then 0 else current
        end) as new_current
from t;