SQLite Subqueries and Inner Joins - sql

Question

I was doing a practice question for SQL which asks to create a list of album titles and unit prices for the artist "Audioslave" and find out how many records are returned.
Here is the relational database picture given in the question:
Initially, I used an inner join to retrieve the list and actually got the correct answer (40 records returned). The code is shown below:
select a.Title, t.UnitPrice
from albums a
inner join tracks t on t.AlbumId = a.AlbumId
inner join artists ar on ar.ArtistId = a.ArtistId
where ar.Name = 'Audioslave';
Although I finished the question, I was curious to try to solve this problem using nested subqueries instead and tried to first retrieve the AlbumId and UnitPrice from tracks. I got the correct answer but not the correct list (the question asked for album title and not AlbumId). Here is the code:
select AlbumId, UnitPrice
from tracks
where AlbumId in (
select AlbumId
from albums
where ArtistId in (
select ArtistId
from artists
where Name = 'Audioslave'));
In order to solve the problem with the list, I tried combining the previous codes. However, I get a completely different amount of records being returned (10509).
select a.Title, t.UnitPrice
from albums a
inner join tracks t
where a.AlbumId in (
select AlbumId
from albums
where ArtistId in (
select ArtistId
from artists
where Name = 'Audioslave'));
I don't understand what I'm doing wrong with the last code...Any help would be appreciated! Also, sorry if I wrote too much, I just wanted to convey my thinking process clearly.

Answer 1

Some databases (SQLite, MySQL, Maria, maybe others) allow you to write an INNER JOIN without specifying ON, and they just cross every record on the left with every record on the right in that case. If there were 2 albums and 3 tracks, 6 rows would result. If the albums were A and B, and the tracks were 1, 2 and 3, the rows would be the combination of all: A1, A2, A3, B1, B2, B3
Other databases (Postgres, SQLServer, Oracle, maybe others) refuse to do it unless you specify ON. To get an "every row on the left combined with every row on the right" you have to write CROSS JOIN (or write an inner join with an ON that is always true)
It might help your mental model of what happens during a join to consider that the db takes all the rows on the left and connects them to all the rows on the right, then for each combination of rows, assesses the truth of the ON clause, and the WHERE clause, before deciding to return the row
For example, this will return 10509 rows:
SELECT * FROM albums INNER JOIN tracks ON 1=1
The on clause is always true
This will return 10509 tracks, but only if the query is run on Monday
SELECT * FROM albums INNER JOIN tracks ON strftime('%w', 'now') = 1
What goes in the ON or WHERE doesn't have to have anything to do with the data in the table.. it just has to be something that resolves to a Boolean