How to find the record in a table that contains the maximum value?

Question

Although this question looks simple, it is kind of tricky.

I have a table with the following columns:

table A:
  int ID
  float value
  datetime date         


        

Answer 1

As long as the Date column is unique for each group I think something like this might work:

SELECT A.ID, A.Value
FROM A
  INNER JOIN (SELECT Group, MAX(Date) As MaxDate FROM A GROUP BY Group) B
    ON A.Group = B.Group AND A.Date = B.MaxDate

Answer 2

You could try with a subquery

select group, id, value, date from A where date in
( select MAX(date) as date
  from A
  group by group )
order by group

Answer 3

This is just what analytic functions were made for:

select group,
       id,
       value
from   (
       select group,
              id,
              value,
              date,
              max(date) over (partition by group) max_date_by_group
       from A
       )
where  date = max_date_by_group

Answer 4

If date is unique, then you already have your answer. If date is not unique, then you need some other uniqueifier. Absent a natural key, your ID is as good as any. Just put a MAX (or MIN, whichever you prefer) on it:

SELECT *
FROM A
JOIN (
    --Dedupe any non unqiue dates by getting the max id for each group that has the max date
    SELECT Group, MAX(Id) as Id
    FROM A 
    JOIN (
        --Get max date for each group
        SELECT group, MAX(date) as Date 
        FROM A 
        GROUP BY group
    ) as MaxDate ON
        A.Group = MaxDate.Group
        AND A.Date = MaxDate.Date
    GROUP BY Group
) as MaxId ON
    A.Group = MaxId.Group
    AND A.Id= MaxId.Id