需要帮助选择SQL中的distinct和max字段

Question

因此，在nc_sno.netcredit_dist_lp1表中，有贷款编号和ID编号。 每个贷款号最多可以有两个不同的ID号。 我想为每个贷款号提取最高的ID号。 这就是我所拥有的。 感谢您的帮助：

select
  tempkk3.loan_number
,tempkk3.username
, tempkk3.week_number
,lp.lp_rules_instruction as lp_instruction
,lp.insert_timestamp as time_entered_queue
,lp.id
from
  nc_sno.netcredit_dist_lp1 lp
join tempkk3 using (loan_number)

Answer 1

Postgres distinct on功能distinct on有非常不错的distinct on ，它确实可以实现您想要的功能：

select distinct on (loan_number) loan_number,
       tempkk3.username, tempkk3.week_number,
       lp.lp_rules_instruction as lp_instruction,
       lp.insert_timestamp as time_entered_queue,
       lp.id
from nc_sno.netcredit_dist_lp1 lp join
     tempkk3
     using (loan_number)
order by loan_number, id desc;