T-SQL查询以获取具有多个聚合函数的行

Question

I have the following problem. I need to fetch the row for each distinct user_id with the min rank, max end date, max begin date, and max sequence number in that order . Essentially, I want a user's highest ranked, most recent MAJOR_ID . I am trying to avoid making separate temp tables and joining on those aggregate functions like the following:

select USER_ID
    , SEQ_NBR
    , BEGIN_DATE
    , END_DATE
    , MAJOR_RANK
    , MAJOR_ID
    , DEGREE_CODE
into #major0
from majors

select USER_ID
    , MIN(MAJOR_RANK) as MAJOR_RANK
into #major1
from #major0
group by USER_ID

select #major0.USER_ID
    , #major0.MAJOR_RANK
    , MAX(#major0.END_DATE) as END_DATE
into #major2
from #major0
inner join #major1 on #major0.USER_ID = #major1.USER_ID and #major0.MAJOR_RANK = #major1.MAJOR_RANK
group by #major0.USER_ID
    , #major0.MAJOR_RANK

etc...

until I get to that row that satisfies all the criteria, and I join back on all the fields from the original query. Does that make sense? It's a lot of work to write this out, and I can't create a view of it unless I made a absurdly long set of subqueries, I don't think I can utilize MIN(MAJOR_RANK) OVER (PARTITION BY USER_ID) in a subquery for all these fields because I will lose records that don't satisfy all of them.

Any suggestions would help! Thank you!

Answer 1

I do not see what the sequence_number is, but you can most likely solve this using a common table expression with row_number()

;with cte as (
  select 
      user_id
    , begin_date
    , end_date
    , major_rank
    , major_id
    , degree_code
    , rn = row_number() over (
        partition by user_id 
        order by major_rank asc, end_date desc, begin_date desc /*, sequence_number? desc*/
        )
from majors
)
select 
    user_id
  , begin_date
  , end_date
  , major_rank
  , major_id
  , degree_code
from cte
where rn = 1

without the cte

select 
    user_id
  , begin_date
  , end_date
  , major_rank
  , major_id
  , degree_code
from (
  select 
      user_id
    , begin_date
    , end_date
    , major_rank
    , major_id
    , degree_code
    , rn = row_number() over (
        partition by user_id 
        order by major_rank asc, end_date desc, begin_date desc /*, sequence_number? desc*/
        ) 
from majors
) sub
where rn = 1