DISTINCT vs GROUP BY

MySQL & MariaDB Other MySQL® Questions
1

Is there any performance difference between DISTINCT and GROUP BY?

I have a table articles and I want to get unique users who posted the articles. userid has an index. What should I use DISTINCT or GROUP BY? Is there any difference between their performance? I am concerned about the performance.

I need to get only userid from articles. Which one is better?

SELECT DISTINCT userid FROM articles WHERE posted_date BETWEEN ‘2007-01-01’ AND CURDATE();

OR

SELECT userid FROM articles WHERE posted_date BETWEEN ‘2007-01-01’ AND CURDATE() GROUP BY userid;

EXPLAIN is exactly the same for both.

2

It’ll reduce to the same pathway for both, however I prefer to use “GROUP BY” as it seems more logical to me and increases usability IMO.

3

I am looking for some definite answer.

4

There is no performance difference.

Since, as Speeple said, mysql is performing the exact same execution to perform the two queries.

So essentially it is just a matter of syntax in this case, the end result is the same.