SQL nested query returns nothing - mysql

Question

I am a beginner in SQL and am having difficulty understanding the logic query. In this particular problem, I am trying to find the Track that was purchased in California.
Here are the tables.
CREATE TABLE [InvoiceLine]
(
[InvoiceLineId] INTEGER NOT NULL,
[InvoiceId] INTEGER NOT NULL,
[TrackId] INTEGER NOT NULL,
[UnitPrice] NUMERIC(10,2) NOT NULL,
[Quantity] INTEGER NOT NULL,
CONSTRAINT [PK_InvoiceLine] PRIMARY KEY ([InvoiceLineId]),
FOREIGN KEY ([InvoiceId]) REFERENCES [Invoice] ([InvoiceId])
ON DELETE NO ACTION ON UPDATE NO ACTION,
FOREIGN KEY ([TrackId]) REFERENCES [Track] ([TrackId])
ON DELETE NO ACTION ON UPDATE NO ACTION
);
CREATE TABLE [Invoice]
(
[InvoiceId] INTEGER NOT NULL,
[CustomerId] INTEGER NOT NULL,
[InvoiceDate] DATETIME NOT NULL,
[BillingAddress] NVARCHAR(70),
[BillingCity] NVARCHAR(40),
[BillingState] NVARCHAR(40),
[BillingCountry] NVARCHAR(40),
[BillingPostalCode] NVARCHAR(10),
[Total] NUMERIC(10,2) NOT NULL,
CONSTRAINT [PK_Invoice] PRIMARY KEY ([InvoiceId]),
FOREIGN KEY ([CustomerId]) REFERENCES [Customer] ([CustomerId])
ON DELETE NO ACTION ON UPDATE NO ACTION
);
CREATE TABLE [Track]
(
[TrackId] INTEGER NOT NULL,
[Name] NVARCHAR(200) NOT NULL,
[AlbumId] INTEGER,
[MediaTypeId] INTEGER NOT NULL,
[GenreId] INTEGER,
[Composer] NVARCHAR(220),
[Milliseconds] INTEGER NOT NULL,
[Bytes] INTEGER,
[UnitPrice] NUMERIC(10,2) NOT NULL,
CONSTRAINT [PK_Track] PRIMARY KEY ([TrackId]),
FOREIGN KEY ([AlbumId]) REFERENCES [Album] ([AlbumId])
ON DELETE NO ACTION ON UPDATE NO ACTION,
FOREIGN KEY ([GenreId]) REFERENCES [Genre] ([GenreId])
ON DELETE NO ACTION ON UPDATE NO ACTION,
FOREIGN KEY ([MediaTypeId]) REFERENCES [MediaType] ([MediaTypeId])
ON DELETE NO ACTION ON UPDATE NO ACTION
);
Here is what I've tried.
SELECT T.name
FROM Track T, InvoiceLine L
WHERE T.trackid=L.trackid AND
L.invoiceid IN (SELECT I.invoiceid
FROM Invoice I
WHERE I.billingcity="California");
The query returns nothing. What is wrong with the logic?

Answer 1

SELECT
T.name
FROM Track T
INNER JOIN InvoiceLine L ON T.trackid = L.trackid
INNER JOIN invoice I ON L.InvoiceId = I.InvoiceId
WHERE I.BillingState = 'California'
Track joins to InvoiceLine which joins to Invoice
Please do NOT use the ancient way of joining through the where clause. The simplest trick for this is to disallow any commas between table e.g. note the comma in: FROM Track T, InvoiceLine L - avoid those.
I assume you want the state of California held in BillingState not a city of that name (if one exists).