MySQL表 一行数据转多行数据

Posted 2022-02-08 可小辉

原始表如下：

 将原始表转换为：

创建原始数据，SQL如下

create table if not exists splitdata(
id int(10),
name varchar(20),
subject varchar(30));
 
 
insert into splitdata values
(1,'Lily','语文,英语,科学'),
(2,'Lucy','语文,英语'),
(3,'Mary','体育,科学'),
(4,'Olio','数学,体育');
insert into splitdata values(
5,'Loe','["user1","user2","user3"]');

使用mysql自带的表mysql.help_topic里面的help_topic_id这一连续id字段。（无需自创表）

select a.id,a.name,substring_index(substring_index(subject,',',b.help_topic_id + 1),',',-1) subject from(
select id,name,replace(replace(replace(subject,'[',''),']',''),'"','') subject from splitdata) a
join mysql.help_topic b
on b.help_topic_id < length(a.subject) - length(replace(a.subject,',','')) + 1;