Select 行使用 group by 并且在每个组中获取基于另一个列值的最高值的列值

Question

I need to get latest field based on another field in group by we have

Table "SchoolReview"

Id	SchoolId	Review	Point
1	1	rv1	8
2	1	rv2	7
3	2	rv3	4
4	2	rv4	7
5	3	rv5	2
6	3	rv6	8

I need to group by SchoolId and the inside group I need to get Review and Point from highest "Id" column.

I dont need "Id" coulmn but even if I get it for this solution its okay.

Result I am looking for shall look like this.

SchoolId	Review	Point
1	rv2	7
2	rv4	7
3	rv6	8

Any one experienced in MS SQL Server can help in this regard?

Answer 1

You do not need to group the rows, you simply need to select the appropriate rows from the table. In this case, using ROW_NUMBER() is an option:

Table:

SELECT *
INTO Data
FROM (VALUES
   (1, 1, 'rv1', 8),
   (2, 1, 'rv2', 7),
   (3, 2, 'rv3', 4),
   (4, 2, 'rv4', 7),
   (5, 3, 'rv5', 2),
   (6, 3, 'rv6', 8)
) v (Id, SchoolId, Review, Point)

Statement:

SELECT SchoolId, Review, Point
FROM (
   SELECT *, ROW_NUMBER() OVER (PARTITION BY SchoolId ORDER BY Id DESC) AS Rn
   FROM Data
) t
WHERE Rn = 1

Result:

SchoolId Review Point
---------------------
1        rv2    7
2        rv4    7
3        rv6    8

Answer 2

Using sample data from other answer

SELECT *
INTO #Data
FROM (VALUES
   (1, 1, 'rv1', 8),
   (2, 1, 'rv2', 7),
   (3, 2, 'rv3', 4),
   (4, 2, 'rv4', 7),
   (5, 3, 'rv5', 2),
   (6, 3, 'rv6', 8)
) v (Id, SchoolId, Review, Point)

SELECT S.SchoolId,
       S.Review,
       S.Point 
FROM   #Data S
INNER JOIN
(
    SELECT Id = MAX(S1.Id),
           S1.SchoolId
    FROM   #Data S1
    GROUP BY SchoolId
) X ON X.Id = S.Id AND X.schoolId = S.SchoolId
ORDER BY X.SchoolId    
;

output