Mysql中substring_index函数实现字符分割一行变多行

create table tb_staff_position_info
(
    id                 varchar(255)                           not null comment '主键'
        primary key,
    created_at         timestamp    default CURRENT_TIMESTAMP not null comment '记录创建时间',
    updated_at         timestamp    default CURRENT_TIMESTAMP not null on update CURRENT_TIMESTAMP comment '记录修改时间',
   staff_name    varchar(64)  default ''                not null comment '员工名称',
   position_name    varchar(64)  default ''                not null comment '多个职位以,号分割',
  
)
    comment '员工职位表' charset = utf8;

insert into tb_staff_position_info(staff_name,position_name)values
('小平','技术组长,产品经理,项目经理'),('小花','程序员,测试员,'),('小广‘,'研发总监')

select 
  info.staff_name,
  substring_index(
        substring_index(
            info.position_name ,
            ',',
            b.n + 1
        ),
        ',' ,- 1
    ) AS position_name
  from tb_staff_position_info info
  join mysql.help_topic b  
on b.help_topic_id < ( length(info.position_name ) - length(REPLACE (info.position_name , ',', ''))  + 1 ) 

select 
  info.staff_name,
  substring_index(
        substring_index(
            info.position_name ,
            ',',
            b.n + 1
        ),
        ',' ,- 1
    ) AS position_name
  from tb_staff_position_info info
  join (
          select 0 as n
          union all 
          select 1 as n
          union all 
          select 2 as n
          ) b 
         on b.n < ( length(info.position_name ) - length(REPLACE (info.position_name , ',', ''))  + 1 )