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

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。

以下是我当前正在尝试的查询，但存在重复记录：

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 

推荐答案

On选项是使用子查询进行筛选：

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
)

为提高性能，请考虑table1(vehid, requestCreateDate)上的索引。

您还可以使用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

这篇关于最新记录MS SQL的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！