SQL-Chinnok-Database

Query the Chinook Database to help the team at Chinook music store understand the media in their store, their customers and employees, and their invoices information

Table of contents

• Introduction
• Chinnok Database
• Intructions
• Queries
• References

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Introduction

In this lab, you will query the Chinook Database. The Chinook Database holds information about a music store. For this lab, you will be answering 5 queries to help the Chinook team understand the media in their store, their customers and employees, and their invoice information. To assist you in the queries ahead, the schema for the Chinook Database is provided below. You can see the columns that link tables together via the arrows.

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Chinnok Database

Below you can see the Schema of Chinnok Database:

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Instruction

In order to help the team at Chinook music store, you need to answer the following 5 queries

• Q1 Use the Invoice table to determine the countries that have the most invoices. Provide a table of BillingCountry and Invoices ordered by the number of invoices for each country. The country with the most invoices should appear first.
• Q2 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.

check your solution: The top city for Invoice dollars was Prague with an amount of 90.24

• Q3 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. I found the solution by linking the following three: Invoice, InvoiceLine, and Customer tables to retrieve this information, but you can probably do it with fewer!

check your solution: The customer who spent the most according to invoices was Customer 6 with 49.62 in purchases.

• Q4 The team at Chinook would like to identify all the customers who listen to Rock music. Write a 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'.

Check your solution: Your final table should have 59 rows and 4 columns.

• Q5 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.

Check Your Solution: Though there are only 24 countries, your query should return 25 rows because the United Kingdom has 2 customers that share the maximum.

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Queries

• Q1 :

SELECT BillingCountry, COUNT(*) AS invoices_number
FROM Invoice
GROUP BY 1
ORDER BY 2 DESC

• Q2:

SELECT BillingCity, SUM(Total) AS invoices_total
FROM Invoice
GROUP BY 1
ORDER BY 2 DESC
LIMIT 1

• Q3:

SELECT c.CustomerId,
       c.FirstName,
       c.LastName,
       sum(inv.UnitPrice) AS invoices
FROM Invoice i
JOIN InvoiceLine il
ON il.Invoiceid = i.Invoiceid
JOIN Customer c
ON c.CustomerId = i.CustomerId
GROUP BY 1,2,3
ORDER BY i.Total DESC
LIMIT 1

• Q4:

SELECT c.Email,
       c.FirstName,
       c.LastName,
       g.Name
FROM Customer c
JOIN Invoice i
ON c.CustomerId= i.CustomerId
JOIN InvoiceLine il
ON i.InvoiceId= il.InvoiceId
JOIN Track t
ON t.TrackId = il.TrackId
JOIN Genre g
ON g.GenreId = t.GenreId
WHERE g.Name = 'Rock'
GROUP BY 1

• Q5:

WITH c AS (SELECT Invoice.CustomerId AS id_cst, 
                 Invoice.BillingCountry AS Country, 
                 SUM(Invoice.Total) AS som 
           FROM Invoice
           JOIN Customer 
           ON Invoice.BillingCountry = Customer.Country AND Invoice.CustomerId = Customer.CustomerId
           GROUP BY 1,2
           ORDER BY 2 ),
          
    Customers AS (SELECT Customer.CustomerId as cust_id, 
                         Customer.FirstName as name_customer, 
                         Customer.LastName as lastname_customer 
              FROM Customer)

SELECT customers.cust_id, 
       customers.name_customer,
       customers.lastname_customer, 
       b.country, 
       b.max_som 
FROM Customers, (SELECT a.country AS country, 
                        max(a.som) AS max_som 
                 FROM (SELECT Invoice.CustomerId AS id_cst, 
                              Invoice.BillingCountry AS Country, 
                              SUM(Invoice.Total) AS som 
                       FROM Invoice 
                       JOIN Customer 
                       ON Invoice.BillingCountry = Customer.Country AND Invoice.CustomerId = Customer.CustomerId
                       GROUP BY 1,2
                       ORDER BY 2 ) AS a
                 GROUP BY 1
                 ORDER BY 2 ) AS b
JOIN c
ON c.country = b.country AND c.som = b.max_som
WHERE Customers.cust_id = c.id_cst

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References

• Data Analyst Track

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Author Infos

• LinkedIn - Nour Eddine ZEKAOUI
• View my verified achievement here from Udacity

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What are you waiting for to enroll for the track and try it for yourself. You'll enjoy uncovering insights from data in an efficient way!

Thank you for your intrest ☻

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