SQLite3 Query COUNT combining two tables - database

Question

I'm having trouble trying to get my query working as intended, I have two tables (names and classes). Where names has two rows (username and name) & classes has three rows (class, username and time).
I'm trying to extract username, name and the amount of classes each person teaches (see table below), which can be figured out by looking at how many times a given "username" appears in the "classes" table. The problem is that there are some usernames that appear in the "names" table but don't appear in the "classes" table, these users should be assigned "0" in the count. There's also users who appear in the classes table but don't appear in the names table, these people should still be taken into account but with a null value as their name.
names table classes table
__________________ ________________________
|username | name | |class | username |time |
|ab | Ali | |xxx | ch |xxx |
|ch | Chi | |xxx | dd |xxx |
|dd | Dia | |xxx | ee |xxx |
etc...
desired output from query
__________________________________________
|username | name |number of classes taught|
|ab | Ali |0 |
|ch | Chi |1 |
|dd | Dia |3 |
|ee | null |5 |
etc....
I have the following query so far
SELECT
names.username,
name,
COUNT(*)
FROM
classes
INNER JOIN names ON
names.username = classes.username
GROUP BY
classes.username
ORDER BY
COUNT(*)
actual output from query
__________________________________________
|username | name |number of classes taught|
|ch | Chi |1 |
|dd | Dia |3 |
But this gives me an output that doesn't include users who don't teach and also excludes users who don't have a real name. I'm not sure how to resolve this issue, would I need to combine the two username rows without creating duplicates? or something along those lines?

Answer 1

If you want all users, start with the user table. If you want all users that don't have any classes, do a LEFT join and not an INNER join
SELECT
names.username,
name,
COUNT(*)
FROM
names
LEFT JOIN classes ON
names.username = classes.username
GROUP BY
classes.username
ORDER BY
COUNT(*)

Answer 2

What you need is a FULL OUTER join which is not supported by SQLite, but can be emulated with LEFT joins and UNION ALL and then aggregate:
select username, name, count(*) [number of classes taught]
from (
select n.username, n.name, c.class
from names n left join classes c
on c.username = n.username
union all
select c.username, n.name, c.class
from classes c left join names n
on c.username = n.username
where n.username is null
)
group by username, name
See a simplified demo.