SELECT <fields>  
FROM <TABLES>  
WHERE <criteria>  
ORDER BY <order>  

INSERT <table> (<fields>)  
VALUES (<data>)  

UPDATE <table>  
SET <field> = <data>  
WHERE <criteria>  

DELETE <table>  
WHERE <criteria>  

SELECT *  
FROM customers  

SELECT company_name, contact_name, contact_title  
FROM customers  

SELECT company_name, contact_name, country  
FROM customers  
WHERE country = 'Sweden'

SELECT product_name, units_in_stock  
FROM products  
WHERE units_in_stock < 10  

SELECT company_name, contact_name, city, country  
FROM customers  
ORDER BY company_name DESC  

SELECT company_name, contact_name, city, country  
FROM customers  
ORDER BY country DESC, city  
 
SELECT company_name, contact_name, city, country  
FROM customers  
WHERE country in ('USA', 'Japan', 'Germany')  
ORDER BY country DESC, city  

SELECT product_id, product_name, unit_price  
FROM products  
ORDER BY unit_price  
LIMIT 5  

SELECT DISTINCT country  
FROM customers  
ORDER BY country  

SELECT MIN(unit_price)  
FROM products  

SELECT *  
FROM products  
WHERE unit_price =  
 (SELECT MAX(unit_price)  
  FROM products)  

SELECT count(*)  
FROM products  

SELECT count(DISTINCT unit_price)  
FROM products  

SELECT quantity_per_unit, count(*)  
FROM products  
GROUP BY quantity_per_unit  

SELECT *  
FROM employees  
WHERE first_name = 'Anne' AND last_name = 'Dodsworth'  

SELECT company_name, city, country  
FROM customers  
WHERE NOT country = 'USA'  

SELECT product_id, product_name, unit_price  
FROM products  
WHERE unit_price between 10 and 20  

SELECT company_name, contact_name, city, country  
FROM suppliers  
WHERE upper(country) in ('USA', 'CANADA', 'MEXICO')  

SELECT company_name, contact_name, city, country  
FROM customers  
WHERE country IN  
    (SELECT country  
     FROM suppliers)  

// all products starting with C  
SELECT product_name  
FROM products  
WHERE product_name LIKE 'C%'  

// no homepage  
SELECT company_name, contact_name, homepage  
FROM suppliers  
WHERE homepage is NULL  

// has homepage  
SELECT company_name, contact_name, homepage  
FROM suppliers  
WHERE homepage is NOT NULL  

// countries with 10 or more customers  
SELECT count(customer_id), country  
FROM customers  
GROUP BY country  
HAVING count(customer_id) > 10  

SELECT COUNT(c.customer_id) as TotalCustomers, c.country as Nation  
FROM customers c  
GROUP BY c.country  
ORDER by TotalCustomers  

// inner join - select records that match in BOTH tables  
// includes those customers with orders and  
// only those orders with customers  

SELECT o.Order_Date, c.Company_Name, c.Contact_Name  
FROM orders o JOIN customers c  
on o.Customer_ID = c.Customer_ID  

SELECT o.Order_Date, c.Company_Name, c.Contact_Name  
FROM orders o, customers c  
WHERE o.Customer_ID = c.Customer_ID  

// Left join - select all records from the left   
// table getting the data from the right table where available.  

// includes all customers and if available their order data  

SELECT o.Order_Date, c.Company_Name, c.Contact_Name  
FROM customers c LEFT JOIN orders o  
ON o.Customer_ID = c.Customer_ID  
ORDER BY o.Order_Date  

// Right join - select all records from the right table  
// getting the data from the left table where available.  

SELECT o.Order_Date, c.Company_Name, c.Contact_Name  
FROM customers c RIGHT JOIN orders o  
ON o.Customer_ID = c.Customer_ID  
ORDER BY o.Order_Date  

// Full Join - select all records from both tables joining the  
// data as appropriate.  

SELECT o.Order_Date, c.Company_Name, c.Contact_Name
FROM customers c INNER JOIN orders o
ON o.Customer_ID = c.Customer_ID
ORDER BY o.Order_Date

http://www.postgresqltutorial.com/postgresql-joins/

// match customers from the same country and city  
SELECT a.company_name, a.contact_name, a.city, a.country  
FROM customers a, customers b  
WHERE a.Customer_ID <> b.Customer_ID  
  AND a.City = b.City  
  AND a.Country = b.Country  
ORDER BY a.country, a.city  

SELECT company_name, contact_name, phone  
FROM customers  
UNION   
SELECT 'Northwind', CONCAT(first_name, ' ', last_name), home_phone  
FROM employees  
ORDER BY company_name 

SELECT company_name, contact_name, city, country  
FROM customers  
WHERE country IN  
    (SELECT country  
     FROM suppliers)  

SELECT contact_name, phone,   
       (SELECT COUNT(o.order_id)   
        FROM orders o   
        WHERE o.customer_id = c.customer_id) as ordercount  
FROM customers c  
ORDER BY ordercount  

// list all suppliers who have products with less than 10 units in stock  
SELECT company_name  
FROM suppliers    
WHERE EXISTS  
 (SELECT product_name  
  FROM products  
  WHERE supplier_id = suppliers.Supplier_ID  
  AND units_in_stock < 10)  

INSERT INTO customers(customer_id, company_name, contact_name)  
VALUES (9191, 'Lambda School', 'John Mitchell')  

INSERT INTO customers(customer_id, company_name, contact_name)  
SELECT 9192, company_name, contact_name  
FROM suppliers  
WHERE company_name LIKE 'BIG%'  

// discontinuing all products with unit price < 10.00  
UPDATE products  
SET discontinued = 1  
WHERE unit_price < 10.00  

UPDATE suppliers  
SET City = 'Oslo', Phone = '(0)1-953530', Fax = '(0)1-953555'  
WHERE supplier_id = 15  

DELETE   
FROM products  
WHERE unit_price < 10.00  

DELETE   
FROM customers  
WHERE customer_id = '15'