INNER JOIN内连接

练习内容

-- 查询用户及其订单信息\nSELECT u.id, u.name, o.order_id, o.amount, o.created_at\nFROM users u\nINNER JOIN orders o ON u.id = o.user_id\nWHERE o.status = 'completed'\nORDER BY o.created_at DESC;\n\n-- 查询产品及其分类信