检索每个顾客的名称和所有的订单号（二）_牛客题霸

Orders表代表订单信息含有订单号order_num和顾客id cust_id order_num cust_id a1 cust10 a2 cust1 a3 cust2 a4 cust22 a5 cust221 a7 cust2217 Customers表代表顾客信息含有顾客id cust_id和顾客名称 cust_name cust_id cust_name cust10 andy cust1 ben cust2 tony cust22 tom cust221 an cust2217 hex cust40 ace 【问题】检索每个顾客的名称（Customers表中的 cust_name）和所有的订单号（Orders 表中的 order_num），列出所有的顾客，即使他们没有下过订单。最后根据顾客姓名cust_name升序返回。【示例结果】返回顾客名称cust_name和订单号order_num cust_name order_num ace NULL an a5 andy a1 ben a2 hex a7 tom a4 tony a3 【示例解析】基于两张表，返回订单号a1的顾客名称andy等人，没有下单的顾客ace也统计了进来

示例1

输入

DROP TABLE IF EXISTS `Customers`;
CREATE TABLE IF NOT EXISTS `Customers`(
	cust_id VARCHAR(255) NOT NULL COMMENT '客户id',
	cust_name VARCHAR(255) NOT NULL COMMENT '客户姓名'
);
INSERT `Customers` VALUES ('cust10','andy'),('cust1','ben'),('cust2','tony'),('cust22','tom'),('cust221','an'),('cust2217','hex'),('cust40','ace');

DROP TABLE IF EXISTS `Orders`;
CREATE TABLE IF NOT EXISTS `Orders`(
  order_num VARCHAR(255) NOT NULL COMMENT '商品订单号',
  cust_id VARCHAR(255) NOT NULL COMMENT '顾客id'
);
INSERT `Orders` VALUES ('a1','cust10'),('a2','cust1'),('a3','cust2'),('a4','cust22'),('a5','cust221'),('a7','cust2217');

输出

ace|None
an|a5
andy|a1
ben|a2
hex|a7
tom|a4
tony|a3