如何获取 SQLAlchemy 和 postgresql 数据库中的最后一次出现？

Question

How to query postgres database to get grouped result with last occurrence?

I have a table like this one:

id | emp_id | hours
1  | 1      | 8
2  | 1      | 6
3  | 2      | 6
4  | 2      | 3
5  | 1      | 5

I want to receive below result:

emp_id | hours
1      | 5
2      | 3

I want it to be ordered descending by id and get last value for each employee.

Answer 1

You probably want to use some group by and do something like:

from sqlalchemy import func
session.query(Table.col_emp_id,func.max(Table.col_hour)).group_by(Table.col_emp_id).all()

I'm not an expert, just a clue

Answer 2

The script below can give you the expected result:

 select emp_id,hours from ( select *, row_number() over(partition by emp_id order by id desc) as rank from <your_table> )tab where tab.rank=1