MySQL中CONCAT() ，CONCAT_WS() ，GROUP_CONCAT()的用法

/*
SQLyog Ultimate v12.3.1 (64 bit)
MySQL - 5.5.60 : Database - test-day
*********************************************************************
*/
 
 
/*!40101 SET NAMES utf8 */;
 
/*!40101 SET SQL_MODE=''*/;
 
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`test-day` /*!40100 DEFAULT CHARACTER SET utf8mb4 */;
 
USE `test-day`;
 
/*Table structure for table `day_sell` */
 
DROP TABLE IF EXISTS `day_sell`;
 
CREATE TABLE `day_sell` (
  `id` bigint(11) NOT NULL AUTO_INCREMENT COMMENT '主键',
  `name` varchar(30) DEFAULT NULL COMMENT '销售人姓名',
  `sell_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '销售时间',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4;
 
/*Data for the table `day_sell` */
 
insert  into `day_sell`(`id`,`name`,`sell_time`) values 
 
(1,'张三','2020-11-21 20:28:08'),
 
(2,'李四','2020-11-20 20:28:16'),
 
(3,'关羽','2020-11-11 20:28:26'),
 
(4,'王五','2020-11-21 20:28:37'),
 
(5,'项羽','2020-10-01 20:28:57'),
 
(6,'刘邦','2020-10-08 20:29:17'),
 
(7,'嬴政','2019-10-01 20:29:32'),
 
(8,'太子丹','2021-01-01 20:29:55');
 
/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

SELECT CONCAT(id,NAME,sell_time) FROM `day_sell` AS s