最新记录 MS SQL答案

【问题标题】：Most recent record MS SQL最新记录 MS SQL
【发布时间】：2020-12-22 01:47:36
【问题描述】：

只需要最近的记录

当前数据：

RequestID   RequestCreateDate         VehID    DeviceNum   ProgramStatus   InvID
1           08/12/2018 13:00:00:212     110       20178      Submitted        A1
2           08/11/2018 11:12:33:322     110       20178      Pending          A1
3           09/08/2018  4:14:28:132     110       Null       Cancelled        A1
4           11/11/2019 10:12:00:123     188       21343      Open             B3
5           12/02/2019 06:15:00:321     188       21343      Submitted        B3

请求结果：

RequestID   RequestCreateDate         VehID    DeviceNum   ProgramStatus   InvID 
3           09/08/2018  4:14:28:132     110       Null       Cancelled        A1
5           12/02/2019 06:15:00:321     188       21343      Submitted        B3

InvID 来自我要加入的表 B。

这是我目前正在尝试但有重复记录的查询：

Select 
    max(t1.RequestID) ReqID,
    max(t1.RequestCreateDate) NewDate,
    t1.VehID,
    t1.DeviceNum,
    t1.ProgramStatus,
    t2.InvID
FROM table1 t1
LEFT JOIN table2 t2 ON t1.VehID = t2.VehID
GROUP BY t1.VehID, t1.DeviceNum, t1.ProgramStatus, t2.InvID

我只需要每个 VehID 的最新记录。谢谢

【问题讨论】：

标签： sql-server datetime left-join greatest-n-per-group window-functions

【解决方案1】：

启用选项是使用子查询进行过滤：

select t1.*, t2.invid
from table1
left join table2 t2 on t1.vehid = t1.vehid
where t1.requestCreateDate = (
    select max(t11.requestCreateDate)
    from table1 t11
    where t11.vehid = t1.vehid
)

为了提高性能，请考虑在table1(vehid, requestCreateDate) 上建立索引。

你也可以使用row_number():

select *
from (
    select t1.*, t2.invid, row_number() over(partition by vehid order by requestCreateDate desc) rn
    from table1
    left join table2 t2 on t1.vehid = t1.vehid
) t
where rn = 1

【讨论】：