---------------------------------------- Question 16 Query ----------------------------------------
SELECT employees.first_name, employees.last_name, COUNT(orders.customer_id) FROM employees INNER JOIN orders ON employees.employee_id=orders.employee_id GROUP BY employees.first_name, employees.last_name HAVING COUNT(DISTINCT orders.customer_id) > 50;
---------------------------------------- Question 16 Results --------------------------------------
 first_name | last_name | count
------------+-----------+-------
 Andrew     | Fuller    |    96
 Janet      | Leverling |   127
 Laura      | Callahan  |   104
 Margaret   | Peacock   |   156
 Nancy      | Davolio   |   123
(5 rows)
---------------------------------------- Question 17 Query ----------------------------------------
SELECT product_name FROM products WHERE unit_price < (SELECT AVG(unit_price) FROM products);
---------------------------------------- Question 17 Results --------------------------------------
           product_name
----------------------------------
 Chai
 Chang
 Aniseed Syrup
 Chef Anton's Cajun Seasoning
 Chef Anton's Gumbo Mix
 Grandma's Boysenberry Spread
 Queso Cabrales
 Konbu
 Tofu
 Genen Shouyu
 Geitost
 Pavlova
 Teatime Chocolate Biscuits
 Sir Rodney's Scones
 Gustaf's Knäckebröd
 Tunnbröd
 Guaraná Fantástica
 NuNuCa Nuß-Nougat-Creme
 Nord-Ost Matjeshering
 Gorgonzola Telino
 Sasquatch Ale
 Steeleye Stout
 Inlagd Sill
 Gravad lax
 Chartreuse verte
 Boston Crab Meat
 Jack's New England Clam Chowder
 Singaporean Hokkien Fried Mee
 Gula Malacca
 Rogede sild
 Spegesild
 Zaanse koeken
 Chocolade
 Maxilaku
 Valkoinen suklaa
 Filo Mix
 Tourtière
 Pâté chinois
 Ravioli Angelo
 Escargots de Bourgogne
 Sirop d'érable
 Louisiana Fiery Hot Pepper Sauce
 Louisiana Hot Spiced Okra
 Laughing Lumberjack Lager
 Scottish Longbreads
 Outback Lager
 Flotemysost
 Röd Kaviar
 Longlife Tofu
 Rhönbräu Klosterbier
 Lakkalikööri
 Original Frankfurter grüne Soße
(52 rows)
---------------------------------------- Question 18 Query ----------------------------------------
SELECT COUNT(DISTINCT orders.employee_id) FROM employees FULL JOIN orders ON employees.employee_id=orders.employee_id WHERE ship_city=city AND ship_address != address;
---------------------------------------- Question 18 Results --------------------------------------
 count
-------
     6
(1 row)
---------------------------------------- Question 19 Query ----------------------------------------
SELECT first_name, last_name, COUNT(DISTINCT customer_id) AS unique_clients, COUNT(*) AS order_count FROM employees FULL JOIN orders ON employees.employee_id=orders.employee_id WHERE order_date >= '1998-01-01'::DATE AND order_date <= '1998-12-31'::DATE GROUP BY employees.first_name, employees.last_name;
---------------------------------------- Question 19 Results --------------------------------------
 first_name | last_name | unique_clients | order_count
------------+-----------+----------------+-------------
 Andrew     | Fuller    |             34 |          39
 Anne       | Dodsworth |             16 |          19
 Janet      | Leverling |             30 |          38
 Laura      | Callahan  |             23 |          31
 Margaret   | Peacock   |             33 |          44
 Michael    | Suyama    |             17 |          19
 Nancy      | Davolio   |             32 |          42
 Robert     | King      |             21 |          25
 Steven     | Buchanan  |             11 |          13
(9 rows)
---------------------------------------- Question 20 Query ----------------------------------------
SELECT COUNT(*) FROM orders WHERE ship_country='Sweden' AND shipped_date BETWEEN order_date AND order_date + INTERVAL '7 day';
---------------------------------------- Question 20 Results --------------------------------------
 count
-------
    15
(1 row)
---------------------------------------- Question 21 Query ----------------------------------------
SELECT products.product_name FROM suppliers FULL JOIN products ON suppliers.supplier_id=products.supplier_id WHERE suppliers.company_name='Leka Trading';
---------------------------------------- Question 21 Results --------------------------------------
         product_name
-------------------------------
 Singaporean Hokkien Fried Mee
 Ipoh Coffee
 Gula Malacca
(3 rows)