add DML home work

vberetar/postgresql/dml.sql

@@ -0,0 +1,42 @@
+INSERT INTO users (id, name, age, email, country, is_active, created_at)
+VALUES (1, 'Alice', 25, 'alice@example.com', 'US', true, '2024-01-10 10:00:00'),
+	(2, 'Bob', 30, 'bob@example.com', 'UK', true, '2024-02-05 09:30:00'),
+	(3, 'Carol', 27, 'carol@example.com', 'US', false, '2024-03-01 15:20:00'),
+	(4, 'Diana', 22, 'diana@GMAIL.com', 'US', true, '2024-01-12 08:15:00'),
+	(5, 'Evan', 35, 'EVAN@example.com', 'UK', true, '2024-01-18 19:40:00'),
+	(6, 'Farida', 29, 'farida@example.com', 'KZ', true, '2024-02-20 11:05:00'),
+	(7, 'George', 31, 'george+test@example.com', 'US', true, '2024-03-05 16:45:00'),
+	(8, 'Helen', 24, NULL, 'UK', false, '2024-03-06 08:20:00'),
+	(9, 'Ivan', 26, 'ivan@example.com', 'RU', true, '2024-01-11 14:30:00'),
+	(10, 'Julia', 28, 'julia@example.com', 'US', true, '2024-03-07 18:05:00');
+
+INSERT INTO products (id, name, category, price, in_stock)
+VALUES (1, 'iPhone 15', 'Электроника', 80000, true),
+	(2, 'Kindle', 'Электроника', 15000, true),
+	(3, 'Кроссовки Nike', 'Одежда', 9000, true),
+	(4, 'Кроссовки NoName', 'Одежда', 3000, false),
+	(5, 'Наушники Pro', 'Электроника', 12000, true),
+	(6, 'Фитнес‑браслет', 'Гаджеты', 6000, true),
+	(7, 'Подарочная карта', 'Сервисы', 1000, true);
+
+INSERT INTO orders (id, user_id, order_date, status)
+VALUES (1, 1, '2025-01-10 12:00:00', 'paid'),
+	(2, 3, '2025-01-12 09:30:00', 'cancelled'),
+	(3, 1, '2025-01-15 18:20:00', 'paid'),
+	(4, 2, '2025-01-20 11:05:00', 'created'),
+	(5, 4, '2025-02-01 17:45:00', 'paid'),
+	(6, 5, '2025-02-10 10:10:00', 'refunded'),
+	(7, 7, '2025-03-01 09:00:00', 'paid'),
+	(8, 9, '2025-03-05 19:30:00', 'paid');
+
+INSERT INTO order_items (order_id, product_id, quantity, price_at_purchase)
+VALUES (1, 1, 1, 78000),
+	(1, 3, 2, 8500),
+	(2, 2, 1, 14000),
+	(3, 5, 1, 11000),
+	(3, 7, 1, 1000),
+	(4, 2, 1, 15000),
+	(5, 6, 1, 6000),
+	(6, 1, 1, 82000),
+	(7, 3, 1, 9000),
+	(8, 4, 2, 2800);