按最近日期更新table1值的table1

Question

我想基于table2更新table1，table2有一个公共字段employee_ID。我总是在table1中有唯一的employee_ID但在table2中它可能包含具有相同employee_ID的重复记录。

我在table2中有另一列插入了modified_date。我想根据employee_id和最近修改日期更新table1员工姓名和table2员工姓名。

我有多列要使用相同类型的条件进行更新。任何想法，到目前为止我都试过。

这是查询，我使用了内连接，

ssql = "Update Table1 INNER JOIN Table2 
ON Table1.employee_id= Table2.employee_id 
SET Table1.type= Table2.type"

任何帮助将不胜感激

Answer 1

尝试此查询

update t1 set t1.employee_name = t2.employee_name from table1 as t1
inner join table2 as t2 on t1.employee_id = t2.employee_id
where t2.Modified_date = (select Max(modified_date) from table2 as tb2 where 
tb2.employee_id = t2.employee_id group by tb2.employee_id)

Answer 2

您需要一个中间步骤将Max（modified_date）与每个employee_id相关联。

使用CTE表达式，你可以尝试这样的事情：

with
more_recent as (
    select
        employee_id,
        Max(modified_date) max_modified_date
    from
        table2
    group by
        employee_id    
)
update
    t1
set
    t1.employee_name = t2.employee_name
from
    table1 as t1
    inner join more_recent mr on 
        t1.employee_id = mr.employee_id
    inner join table2 as t2 on 
        mr.employee_id = t2.employee_id
        mr.max_modified_date = t2.modified_date