Project Brief: E-Commerce Database

In this project, you will work with an e-commerce database. The database has products that consumers can buy from different suppliers. Customers can create an order and add several products in one order.

Learning Objectives

• Use SQL queries to retrieve specific data from a database
• Draw a database schema to visualize relationships between tables
• Label database relationships defined by the REFERENCES keyword in CREATE TABLE commands

Requirements

Setup

To prepare your environment, open a terminal and create a new database called cyf_ecommerce:

createdb cyf_ecommerce

Import the file cyf_ecommerce.sql in your newly created database:

psql -d cyf_ecommerce -f cyf_ecommerce.sql

Understand the schema

Open the file cyf_ecommerce.sql in VSCode and examine the SQL code. Take a piece of paper and draw the database with the different relationships between tables (as defined by the REFERENCES keyword in the CREATE TABLE commands). Identify the foreign keys and make sure you understand the full database schema.

Don't skip this step. You may one day be asked at interview to draw a database schema. Sketching systems is a valuable skill for back end developers and worth practising. If you're interested in systems design, you may also want to take a course on Udemy.

You can even draw relationship diagrams on GitHub:

erDiagram
    customers {
        id INT PK
        name VARCHAR(50) NOT NULL
    }
    customers ||--o{ orders : places

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Query Practice

Write SQL queries to complete the following tasks:

• List all the products whose name contains the word "socks".

SELECT * FROM products
WHERE  product_name ILIKE '%socks%';

• List all the products which cost more than 100 showing product id, name, unit price, and supplier id.

SELECT     p.id AS product_id, p.product_name, pa.unit_price, pa.supp_id AS supplier_id
FROM products p
JOIN product_availability pa ON p.id = pa.prod_id
WHERE pa.unit_price > 100;

• List the 5 most expensive products.

SELECT * FROM product_availability
Order BY unit_price desc
LIMIT 5;

• List all the products sold by suppliers based in the United Kingdom. The result should only contain the columns product_name and supplier_name.

SELECT p.product_name, s.supplier_name
FROM products p
JOIN product_availability pa ON p.id = pa.prod_id
JOIN suppliers s ON pa.supp_id = s.id
WHERE s.country = 'United Kingdom';

• List all orders, including order items, from customer named Hope Crosby.

SELECT * FROM order_items oi
JOIN orders o ON oi.id = o.customer_id
JOIN customers c ON o.customer_id = c.id
WHERE c.name  = 'Hope Crosby';

• List all the products in the order ORD006. The result should only contain the columns product_name, unit_price, and quantity.

SELECT p.product_name, pa.unit_price, oi.quantity
FROM product_availability pa
JOIN products p ON pa.prod_id = p.id
JOIN order_items oi ON p.id = oi.product_id
JOIN orders o ON oi.order_id = o.id
WHERE o.order_reference = 'ORD006';

• List all the products with their supplier for all orders of all customers. The result should only contain the columns name (from customer), order_reference, order_date, product_name, supplier_name, and quantity

SELECT c.name, o.order_reference, o.order_date, p.product_name, s.supplier_name, oi.quantity
FROM customers c 
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id 
JOIN products p ON oi.product_id = p.id
JOIN suppliers s ON oi.supplier_id = s.id
ORDER BY order_date, c.name;

Acceptance Criteria

• The cyf_ecommerce database is imported and set up correctly
• The database schema is drawn correctly to visualize relationships between tables
• The SQL queries retrieve the correct data according to the tasks listed above
• The pull request with the answers to the tasks is opened on the main branch of the E-Commerce repository