MySQL与Oracle 转换问题

哪位大佬帮忙，把这个转换成MySQL语句：

SELECT REGEXP_SUBSTR("1,2,3",
'[^,]+',
1,
rownum) as model_id
FROM DUAL
CONNECT BY ROWNUM <= LENGTH("1,2,3") -
LENGTH(REPLACE("1,2,3",',','')) + 1;

可以参考下 https://blog.csdn.net/pjymyself/article/details/81668157

        select SUBSTRING_INDEX(SUBSTRING_INDEX('1,2,3', ',', help_topic_id+1),',', -1) 
        from mysql.help_topic
        where 
        help_topic_id < LENGTH('1,2,3')-LENGTH(REPLACE('1,2,3',',',''))+1