Here\'s a simplified example of what I\'m talking about:
Table: students exam_results
_____________ ____________________________________
| id | name |
Answering the EDITED question (i.e. to get associated columns as well).
In Sql Server 2005+, the best approach would be to use a ranking/window function in conjunction with a CTE, like this:
with exam_data as
(
select r.student_id, r.score, r.date,
row_number() over(partition by r.student_id order by r.score desc) as rn
from exam_results r
)
select s.name, d.score, d.date, d.student_id
from students s
join exam_data d
on s.id = d.student_id
where d.rn = 1;
For an ANSI-SQL compliant solution, a subquery and self-join will work, like this:
select s.name, r.student_id, r.score, r.date
from (
select r.student_id, max(r.score) as max_score
from exam_results r
group by r.student_id
) d
join exam_results r
on r.student_id = d.student_id
and r.score = d.max_score
join students s
on s.id = r.student_id;
This last one assumes there aren't duplicate student_id/max_score combinations, if there are and/or you want to plan to de-duplicate them, you'll need to use another subquery to join to with something deterministic to decide which record to pull. For example, assuming you can't have multiple records for a given student with the same date, if you wanted to break a tie based on the most recent max_score, you'd do something like the following:
select s.name, r3.student_id, r3.score, r3.date, r3.other_column_a, ...
from (
select r2.student_id, r2.score as max_score, max(r2.date) as max_score_max_date
from (
select r1.student_id, max(r1.score) as max_score
from exam_results r1
group by r1.student_id
) d
join exam_results r2
on r2.student_id = d.student_id
and r2.score = d.max_score
group by r2.student_id, r2.score
) r
join exam_results r3
on r3.student_id = r.student_id
and r3.score = r.max_score
and r3.date = r.max_score_max_date
join students s
on s.id = r3.student_id;
EDIT: Added proper de-duplicating query thanks to Mark's good catch in comments
Using MS SQL Server:
SELECT name, score, date FROM exam_results
JOIN students ON student_id = students.id
JOIN (SELECT DISTINCT student_id FROM exam_results) T1
ON exam_results.student_id = T1.student_id
WHERE exam_results.id = (
SELECT TOP(1) id FROM exam_results T2
WHERE exam_results.student_id = T2.student_id
ORDER BY score DESC, date ASC)
If there is a tied score, the oldest date is returned (change date ASC
to date DESC
to return the most recent instead).
Output:
Jim 93 2009-01-03 00:00:00.000
Joe 27 2009-04-09 00:00:00.000
Jay 100 2009-01-06 00:00:00.000
Test bed:
CREATE TABLE students(id int , name nvarchar(20) );
CREATE TABLE exam_results(id int , student_id int , score int, date datetime);
INSERT INTO students
VALUES
(1,'Jim'),(2,'Joe'),(3,'Jay')
INSERT INTO exam_results VALUES
(1, 1, 73, '8/1/09'),
(2, 1, 93, '9/2/09'),
(3, 1, 93, '1/3/09'),
(4, 2, 27, '4/9/09'),
(5, 2, 17, '8/9/09'),
(6, 3, 100, '1/6/09')
SELECT name, score, date FROM exam_results
JOIN students ON student_id = students.id
JOIN (SELECT DISTINCT student_id FROM exam_results) T1
ON exam_results.student_id = T1.student_id
WHERE exam_results.id = (
SELECT TOP(1) id FROM exam_results T2
WHERE exam_results.student_id = T2.student_id
ORDER BY score DESC, date ASC)
On MySQL, I think you can change the TOP(1) to a LIMIT 1 at the end of the statement. I have not tested this though.
SELECT s.name,
COALESCE(MAX(er.score), 0) AS high_score
FROM STUDENTS s
LEFT JOIN EXAM_RESULTS er ON er.student_id = s.id
GROUP BY s.name
With Oracle's analytic functions this is easy:
SELECT DISTINCT
students.name
,FIRST_VALUE(exam_results.score)
OVER (PARTITION BY students.id
ORDER BY exam_results.score DESC) AS score
,FIRST_VALUE(exam_results.date)
OVER (PARTITION BY students.id
ORDER BY exam_results.score DESC) AS date
FROM students, exam_results
WHERE students.id = exam_results.student_id;
Select Name, T.Score, er. date
from Students S inner join
(Select Student_ID,Max(Score) as Score from Exam_Results
Group by Student_ID) T
On S.id=T.Student_ID inner join Exam_Result er
On er.Student_ID = T.Student_ID And er.Score=T.Score
Try this,
Select student.name, max(result.score) As Score from Student
INNER JOIN
result
ON student.ID = result.student_id
GROUP BY
student.name