find_by_sql 呈现一个数组

使用 find_by_sql 方法可以实现对数据库的自定义查询，并将查询结果呈现为一个数组。这个方法在Rails框架中非常常见，它允许我们使用原始的 SQL 语句来查询数据库，从而获得比 ActiveRecord 查询更大的灵活性。

ruby
sql = "SELECT * FROM users WHERE age > 18"
results = User.find_by_sql(sql)
results.each do |user|
  puts user.name
end

ruby
sql = "SELECT products.name, SUM(order_items.quantity * order_items.price) AS total_sales
       FROM products
       INNER JOIN order_items ON products.id = order_items.product_id
       INNER JOIN orders ON order_items.order_id = orders.id
       WHERE orders.status = 'completed'
       GROUP BY products.id
       ORDER BY total_sales DESC"
results = Product.find_by_sql(sql)
results.each do |product|
  puts "#{product.name}: #{product.total_sales}"
end