SQL Server FETCH NEXT X ONLY based on a specific column - sql

Question

I have a request to get some online courses.
This is an example of results I can get :
course_code | course_date | participant_name
------------+-------------+------------------
21175A | 2021-12-01 | Jon Doe
21175A | 2021-12-01 | Lisa Tia
21175A | 2021-13-01 | Jon Doe
21175A | 2021-13-01 | Lisa Tia
As you can see, I get multiple rows for the same course depending on the dates and the participants, so I have to do some process in PHP to put everything in an array with keys (course_code)
I want to make a pagination to get the 25 first courses (and not rows)
SELECT course_code, course_date, participant_name
FROM courses
ORDER BY course_date
OFFSET 0
FETCH NEXT 25 ROWS ONLY
This won't work because a course can take multiple rows (4 here). So I wonder if I can write a query to get the 25 first courses (based on the column course_code) even if there are 100 rows.
Do you have an idea ? Thank you in advance
EDIT : This is what I did :
WITH cte AS
(
SELECT course_code
FROM courses
WHERE course_date <= '2021-12-31'
ORDER BY course_code
OFFSET 0 ROWS
FETCH NEXT 25 ROWS ONLY
)
SELECT *
FROM courses
INNER JOIN cte ON cte.course_code = courses.course_code
WHERE course_date <= '2021-12-31'
I added the WHERE clause in both to make the request slower

Answer 1

Use DENSE_RANK:
WITH cte AS (
SELECT *, DENSE_RANK() OVER (ORDER BY course_code) dr
FROM courses
)
SELECT course_code, course_date, participant_name
FROM cte
WHERE dr <= 25
ORDER BY course_date;
For the pagination part, just change the inequality in the WHERE clause. For example, to get the second page of 25 courses per page, you would use WHERE dr > 25 AND dr <= 50.