Introduction to SQL for everyone part I

intro_to_sql.sql

-- SELECT clause to select specific columns
-- Select all columns from customers table
SELECT * FROM customers;

-- Select firstname, lastname and address columns from customers table
SELECT firstname, lastname, address FROM customers;

-- Use AS (alias) to change the column name
SELECT 
  firstname AS customer_firstname, 
  lastname AS customer_lastname
FROM
  customers;
  
-- Calculate new columns
SELECT revenue - expenditure AS profit
FROM finances; 

-- WHERE clause to filter rows 
-- Select customers who live in Thailand
SELECT * FROM customers
WHERE country = 'Thailand'; 

-- Select customers who live in Thailand or Canada
SELECT * FROM customers
WHERE country = 'Thailand' OR country = 'Canada';