Question

我想找到每位员工的独特评论（按年份），仅显示最近的评论（按年份）

Employee List                 Employee Reviews
Number | Employee Name        GUID | Number | Year
1234     John                 x5848  1234     2016
4526     Jim                  xd565  1234     2015
1123     Pam                  cr484  1123     2016

需要的结果：

Number | Name | GUID | Year
1234     John   x5848  2016
1123     Pam    cr484  2016

我无法弄清楚如何编写一个可以返回上述结果的SQL查询。任何人都有这样或类似的查询经验吗？

Answer 1

您可以通过向其提供行号来对记录进行排名：

select 
  guid, number, year, 
  row_number() over (partition by number order by year desc) as rn
from employee_reviews;

这为每位员工（order by year desc）第1行提供了最新记录（partition by number）。因此：

select emp.number, emp.name, rev.guid, rev.year
from employee amp
join
(
  select 
    guid, number, year, 
    row_number() over (partition by number order by year desc) as rn
  from employee_reviews
) rev on rev.number = emp.number and rev.rn = 1;

两个表上的SQL独特查询

1 个答案: