[SOLVED] When running the query in Sqlite, I get the answer as 9.9. But that is not the correct answer

When running the query in Sqlite, I get the answer as 9.9. But that is not the correct answer

[https://www.sqlitetutorial.net/sqlite-sample-database/]

I wrote this code to get the answer to 'What is the total price for the album “Big Ones”?'

SELECT  al.Title, i.Total, tr.albumid, SUM(tr.UnitPrice)
FROM ((((artists ar INNER JOIN albums al ON ar.ArtistId = al.ArtistId)
INNER JOIN tracks tr ON al.AlbumId = tr.AlbumId)
INNER JOIN invoice_items ii ON tr.TrackId = ii.TrackId)
INNER JOIN invoices i ON ii.invoiceid = i.invoiceid)
WHERE al.Title = 'Big Ones'

I got the SUM(tr.UnitPrice) as 9.9.

But 9.9 is wrong. What should be the correct answer?

Tables from Chinook database is used. The link is provided above.

Solution

You must sum the unit prices of all the tracks of the album, so only 2 tables are needed: albums and tracks.
Join them, and aggregate:

select a.title, 
       sum(t.unitprice) total_price
from albums a inner join tracks t 
on t.albumid = a.albumid
where a.title = 'Big Ones'
group by a.title

You can get the same result even if you omit the group by clause.