SQL. How to find out which ref_id how many times are repeated?

Question

MySQL

Good afternoon, there is a Users table

. There are fields in it: id and ref_id
id - a unique number of each user
ref_id - referrer id (may be NULL if no one invited the user)

The task is this:
You need to make a query that will display the top users who invited the most people (display id and number of referrals)

referrer - a person who invites users to the system
referral - a person who was invited

Thank you in advance for your help!

Answer 1

Like this?

SELECT id as refer, count(ref_id) as refers_count
FROM users
WHERE
ref_id is not null
GROUP BY ref_id
ORDER BY 2 DESC LIMIT 5;

Answer 2

Select ID, count(refer ID)
From table
Group buy ID