Question

Suppose I have a MySQL table with just 2 columns:

id
invited_by_id

and I want to know for
each id how many times it appears in invited_by_id column.

How to make this using only one query?

Answer 1

A simple GROUP BY on the invited_by_id column is all you need, since it holds the same id values as the id column:

SELECT invited_by_id, COUNT(*) AS invited_count FROM table GROUP BY invited_by_id