SELECT orders.order_id, customers.customer_name FROM orders INNER JOIN customers ON orders.customer_id = customers.customer_id; Subqueries: A query nested inside another query (in SELECT , FROM , or WHERE ).
SELECT product_name, price FROM products WHERE price > (SELECT AVG(price) FROM products); Temporary named result sets (using WITH ) for cleaner, more readable queries.
WITH high_value_orders AS ( SELECT customer_id, SUM(amount) AS total FROM orders GROUP BY customer_id HAVING SUM(amount) > 1000 ) SELECT * FROM high_value_orders; The CASE expression works like an if-then-else statement.
Drainage Swansea