更新 SQL Server 中的另一个行值

Posted 2023-03-31

【中文标题】更新 SQL Server 中的另一个行值

【英文标题】：Update another row value in SQL Server

【发布时间】：2020-07-29 14:43:30

【问题描述】：

我有一张表，其名称、位置、开始日期和结束日期如下：

+------+----------+-----------+-----------+-----------+
| name | location | startdate |  endate   | is_active |
+------+----------+-----------+-----------+-----------+
| A    | delhi    | 3/26/2019 | 3/26/2019 |         1 |
| A    | delhi    | 3/27/2019 | 3/27/2019 |         1 |
| A    | delhi    | 3/28/2019 | 3/28/2019 |         1 |
| A    | delhi    | 3/31/2019 | 3/31/2019 |         1 |
+------+----------+-----------+-----------+-----------+

需要像这样更新：

+------+----------+-----------+-----------+-----------+
| name | location | startdate |  endate   | is_active |
+------+----------+-----------+-----------+-----------+
| A    | delhi    | 3/26/2019 | 3/28/2019 |         1 |
| A    | delhi    | 3/27/2019 | 3/27/2019 |         0 |
| A    | delhi    | 3/28/2019 | 3/28/2019 |         0 |
| A    | delhi    | 3/31/2019 | 3/31/2019 |         1 |
+------+----------+-----------+-----------+-----------+

如果startdate 是连续的，则将结束日期更新为最后一个连续的startdate 的结束日期，同时更新is_active = 0 的连续开始日期

【问题讨论】：

请尝试重新格式化您的示例数据，使其更易读。我认为这样会更容易提供帮助。

【参考方案1】：

这是一个孤岛问题。这是一种使用lag() 和累积sum() 来定义组的方法。最后一步是条件逻辑：

select 
    name,
    location,
    startdate,
    case when row_number()  over(partition by name, location, grp order by startdate) = 1 
        then max(startdate) over(partition by name, location, grp) 
        else enddate
    end as enddate,
    case when row_number()  over(partition by name, location, grp order by startdate) = 1 
        then 1 
        else 0
    end as is_active
from (
    select 
        t.*, 
        sum(case when startdate = dateadd(day, 1, lag_enddate) then 0 else 1 end) 
            over(partition by name, location order by startdate) grp
    from (
        select 
            t.*, 
            lag(enddate) over(partition by name, location order by startdate) lag_enddate
        from mytable t
    ) t
) t

Demo on DB Fiddle：

姓名 |位置 |开始日期 |结束日期 |活跃 :--- | :------- | :--------- | :--------- | --------: 一个 |德里| 2019-03-26 | 2019-03-28 | 1 一个 |德里| 2019-03-27 | 2019-03-27 | 0 一个 |德里| 2019-03-28 | 2019-03-28 | 0 一个 |德里| 2019-03-31 | 2019-03-31 | 1