DIGITAL MUSIC STORE PROJECT /***** 05. SQL: Question Set 1 *****/

/* Question 1: Which countries have the most Invoices?*/

SELECT billing_country,COUNT(billing_country) AS Invoice_Number FROM invoice GROUP BY billing_country ORDER BY Invoice_Number DESC;

/* Question 2: Which city has the best customers? We would like to throw a promotional Music Festival in the city we made the most money. Write a query that returns the 1 city that has the highest sum of invoice totals. Return both the city name and the sum of all invoice totals.*/

SELECT billing_city,SUM(total) AS InvoiceTotal FROM invoice GROUP BY billing_city ORDER BY InvoiceTotal DESC LIMIT 1;

/Question 3: Who is the best customer? The customer who has spent the most money will be declared the best customer. Build a query that returns the person who has spent the most money. Invoice, InvoiceLine, and Customer tables to retrieve this information/

SELECT customer.customer_id, first_name, last_name, SUM(total) AS total_spending FROM customer JOIN invoice ON customer.customer_id = invoice.customer_id GROUP BY (customer.customer_id) ORDER BY total_spending DESC LIMIT 1;

/***** 06. SQL: Question Set 2 *****/

/Question 1: Use your query to return the email, first name, last name, and Genre of all Rock Music listeners. Return your list ordered alphabetically by email address starting with A./

/Sol 1:/ SELECT DISTINCT email,first_name, last_name FROM customer JOIN invoice ON customer.customer_id = invoice.customer_id JOIN invoiceline ON invoice.invoice_id = invoiceline.invoice_id WHERE track_id IN( SELECT track_id FROM track JOIN genre ON track.genre_id = genre.genre_id WHERE genre.name LIKE 'Rock' ) ORDER BY email;

/Sol2:/ SELECT DISTINCT email AS Email,first_name AS FirstName, last_name AS LastName, genre.name AS Name FROM customer JOIN invoice ON invoice.customer_id = customer.customer_id JOIN invoiceline ON invoiceline.invoice_id = invoice.invoice_id JOIN track ON track.track_id = invoiceline.track_id JOIN genre ON genre.genre_id = track.genre_id WHERE genre.name LIKE 'Rock' ORDER BY email;

/Question 2: Who is writing the rock music? Now that we know that our customers love rock music, we can decide which musicians to invite to play at the concert. Let's invite the artists who have written the most rock music in our dataset. Write a query that returns the Artist name and total track count of the top 10 rock bands./

SELECT artist.artist_id, artist.name,COUNT(artist.artist_id) AS number_of_songs FROM track JOIN album ON album.album_id = track.album_id JOIN artist ON artist.artist_id = album.artist_id JOIN genre ON genre.genre_id = track.genre_id WHERE genre.name LIKE 'Rock' GROUP BY artist.artist_id ORDER BY number_of_songs DESC LIMIT 10;

/Question 3 First, find which artist has earned the most according to the InvoiceLines? Now use this artist to find which customer spent the most on this artist. For this query, you will need to use the Invoice, InvoiceLine, Track, Customer, Album, and Artist tables. Notice, this one is tricky because the Total spent in the Invoice table might not be on a single product, so you need to use the InvoiceLine table to find out how many of each product was purchased, and then multiply this by the price for each artist./

WITH tbl_best_selling_artist AS( SELECT artist.artist_id AS artist_id,artist.name AS artist_name,SUM(invoiceline.unit_price*invoiceline.quantity) AS total_sales FROM invoiceline JOIN track ON track.track_id = invoiceline.track_id JOIN album ON album.album_id = track.album_id JOIN artist ON artist.artist_id = album.artist_id GROUP BY 1 ORDER BY 3 DESC LIMIT 1 )

SELECT bsa.artist_name,SUM(il.unit_price*il.quantity) AS amount_spent,c.customer_id,c.first_name,c.last_name FROM invoice i JOIN customer c ON c.customer_id = i.customer_id JOIN invoiceline il ON il.invoice_id = i.invoice_id JOIN track t ON t.track_id = il.track_id JOIN album alb ON alb.album_id = t.album_id JOIN tbl_best_selling_artist bsa ON bsa.artist_id = alb.artist_id GROUP BY 1,3,4,5 ORDER BY 2 DESC;

/**** 07. (Advanced) SQL: Question Set 3 *****/

/Question 1: We want to find out the most popular music Genre for each country. We determine the most popular genre as the genre with the highest amount of purchases. Write a query that returns each country along with the top Genre. For countries where the maximum number of purchases is shared return all Genres./

/sales for each country/ SELECT COUNT(*) AS purchases_per_genre, customer.country, genre.name, genre.genre_id FROM invoiceline JOIN invoice ON invoice.invoice_id = invoiceline.invoice_id JOIN customer ON customer.customer_id = invoice.customer_id JOIN track ON track.track_id = invoiceline.track_id JOIN genre ON genre.genre_id = track.genre_id GROUP BY 2,3,4 ORDER BY 2;

/*max genre for each country */ SELECT MAX(purchases_per_genre) AS max_genre_number, country FROM tbl_sales_per_country GROUP BY 2 ORDER BY 2;

/*** Final **/ WITH RECURSIVE tbl_sales_per_country AS( SELECT COUNT() AS purchases_per_genre, customer.country, genre.name, genre.genre_id FROM invoiceline JOIN invoice ON invoice.invoice_id = invoiceline.invoice_id JOIN customer ON customer.customer_id = invoice.customer_id JOIN track ON track.track_id = invoiceline.track_id JOIN genre ON genre.genre_id = track.genre_id GROUP BY 2,3,4 ORDER BY 2 ) ,tbl_max_genre_per_country AS(SELECT MAX(purchases_per_genre) AS max_genre_number, country FROM tbl_sales_per_country GROUP BY 2 ORDER BY 2)

SELECT tbl_sales_per_country.* FROM tbl_sales_per_country JOIN tbl_max_genre_per_country ON tbl_sales_per_country.country = tbl_max_genre_per_country.country WHERE tbl_sales_per_country.purchases_per_genre = tbl_max_genre_per_country.max_genre_number;

/Question 2: Return all the track names that have a song length longer than the average song length. Though you could perform this with two queries. Imagine you wanted your query to update based on when new data is put in the database. Therefore, you do not want to hard code the average into your query. You only need the Track table to complete this query. Return the Name and Milliseconds for each track. Order by the song length with the longest songs listed first./

SELECT name,miliseconds FROM track WHERE miliseconds > ( SELECT AVG(miliseconds) AS avg_track_length FROM track) ORDER BY miliseconds DESC;

/Question 3: Write a query that determines the customer that has spent the most on music for each country. Write a query that returns the country along with the top customer and how much they spent. For countries where the top amount spent is shared, provide all customers who spent this amount. You should only need to use the Customer and Invoice tables./

WITH RECURSIVE tbl_customter_with_country AS ( SELECT customer.customer_id,first_name,last_name,billing_country,SUM(total) AS total_spending FROM invoice JOIN customer ON customer.customer_id = invoice.customer_id GROUP BY 1,2,3,4 ORDER BY 2,3 DESC),

tbl_country_max_spending AS(
	SELECT billing_country,MAX(total_spending) AS max_spending
	FROM tbl_customter_with_country
	GROUP BY billing_country)

SELECT tbl_cc.billing_country, tbl_cc.total_spending,tbl_cc.first_name,tbl_cc.last_name,tbl_cc.customer_id FROM tbl_customter_with_country tbl_cc JOIN tbl_country_max_spending tbl_ms ON tbl_cc.billing_country = tbl_ms.billing_country WHERE tbl_cc.total_spending = tbl_ms.max_spending ORDER BY 1;