如何从两个 SQL 表中获取多个最小值？

Question

我有两个 table，一个 Members table 和一个 Plan table。它们的结构如下。

member   start_date     Mplan               Pplan    version start_dt     end_dt
John     20120701       johnplan           johnplan  1       20120601     20130531
John     20130201       johnplan           johnplan  2       20130601     20140531
John     20130901       johnplan 
John     20131201       johnplan

我需要将 Members table 上的 start_date 更新为 member 的最小值，但在相同的 Plan 版本中.

示例：

20130201 将更改为 20120701，而 20131201 将更改为 20130901。

代码：

UPDATE Members
SET start_date =(
    SELECT MIN(start_date) FROM Members a
        LEFT JOIN Plan ON Mplan = Pplan AND
        start_date BETWEEN start_dt AND end_dt
    WHERE member=a.member
        AND start_date BETWEEN start_dt AND end_dt
)

不幸的是，这会将每个 start_date 设置为 19900101，也就是该列整个 table 中的最低值。

Answer 1

您确实需要将日期转换为日期时间。您将拥有更高的精确度、存储小时、日期和分钟的可能性以及访问日期特定功能、国际转换和本地化。

如果您的列是 Varchar(8)，那么它使用的 space 不会少于 Datetime 列。

也就是说，您要查找的是 row_number()。

类似于：

SELECT Member, MPlan, Start_Date, Row_Number() OVER (PARTITION BY Member, MPLan ORDER BY Start_Date) as Version
FROM Members

Answer 2

你能试试这个吗？我没测试。

With Member_start_dt as
(
    select *, (select start_dt from Pplan where M.start_date <= start_dt AND M.start_date >= end_dt) as Pplan_date
    from Members M
),
Member_by_plan as 
(
    select *, ROW_NUMBER () over (partition by Pplan_date order by start_date) num
    from Member_start_dt
)
update M
Set M.start_date = MBP1.start_date
from  Members M
    inner join Member_by_plan MBP1 ON MBP1.member = M.Member AND num = 1  
    inner join Member_by_plan MBP2 ON MBP2.member = M.Member AND MBP2.Pplan_date = MBP1.Pplan_date AND MBP2.start_date = M.start_date

Answer 3

首先您需要获取特定计划的每个成员的最短开始日期。以下将为您提供。

select MIN(start_date) as min_date,a.member as member_name,a.Mplan as plan_name    FROM Members a inner JOIN [plan] p ON a.Mplan = p.Pplan AND
    start_date BETWEEN p.start_dt AND p.end_dt
    group by a.member, a.Mplan

结果会是这样的。

min_date                member_name plan_name
2012-07-01 00:00:00.000 John        johnplan1
2013-09-01 00:00:00.000 John        johnplan2

使用此选项更新每个成员的计划开始日期，该计划的开始日期是相应计划的最低开始日期。

update members 
set start_date= tbl.min_date from
(SELECT MIN(start_date) as min_date,a.member as member_name,a.Mplan as   plan_name FROM Members a
    inner JOIN [plan] p ON a.Mplan = p.Pplan AND
    start_date BETWEEN p.start_dt AND p.end_dt
    group by a.member, a.Mplan) as tbl
where member=tbl.member_name and Mplan=tbl.plan_name

我创建了您的 2 个表、成员和计划，并使用示例数据测试了此解决方案并且它有效。希望对你有帮助。

如何从两个 SQL 表中获取多个最小值？

how to get multiple min values from two SQL tables?

sql-server

min

sql-update

示例：

代码：