输入SQL查询语句，实时检查语法错误并查看执行结果
SELECT * FROM employees WHERE department = 'Sales';
SELECT o.order_id, c.customer_name, o.order_date FROM orders o JOIN customers c ON o.customer_id = c.customer_id;
SELECT department, COUNT(*) as employee_count, AVG(salary) as avg_salary FROM employees GROUP BY department HAVING COUNT(*) > 5;
SELECT product_name, price FROM products WHERE price > (SELECT AVG(price) FROM products);