SQL - Select 与多列和条件不同

Question

I have a set of data as shown below, how to return results with distinct Set, course_id, exercise_id and test_mode, with the condition of longest testing_name. Many thanks.

Set	course_id	exercise_id	test_mode	testing_name	testing_count
A	5	4	C	test(12)	2
A	5	4	C	test(12) and test(34)	3
A	5	4	P	test(22)	2
A	5	4	B	B	5
A	3	20	C	test(49)	1
A	3	15	B	B	5
B	5	4	B	B	3
B	5	4	P	test(33) and test(87)	3
B	5	4	P	test(88)	1

Expected results:

Set	course_id	exercise_id	test_mode	testing_name	testing_count
A	5	4	C	test(12) and test(34)	3
A	5	4	P	test(22)	2
A	5	4	B	B	5
A	3	20	C	test(49)	1
A	3	15	B	B	5
B	5	4	B	B	3
B	5	4	P	test(33) and test(87)	3

Answer 1

Use ROW_NUMBER here:

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY Set, course_id, exercise_id, test_mode
                                 ORDER BY LENGTH(testing_name) DESC) rn
                                 -- use LEN() for SQL Server
    FROM yourTable
)

SELECT Set, course_id, exercise_id, test_mode, testing_name, testing_count
FROM cte
WHERE rn = 1;