先用数据库拆分出来对应的行

比如oracle里面类似这样

select  regexp_substr(a.REGIONS,'[^,]+',1,level) as REGION,rownum as irow

from (select 'AAA,BBB,CCC,DDD' as REGIONS from dual )a

connect by level <= REGEXP_COUNT(a.REGIONS,'[^,]+')

mysql类似这样

select 

substring_index(

    substring_index(

      t.com,

      ',',

      b.help_topic_id + 1

    ),

    ',' ,- 1

  ) AS com_row,

  t.myname

 from (

select '2021,2019' as com,'张三' as myname 

union all

select '2019' as com,'李四' as myname 

) t 

JOIN mysql.help_topic b ON b.help_topic_id < (

  length(t.com) - length(

    REPLACE (t.com, ',', '')) + 1)

把你的查询语句改成这样就好了

select * from table where ','+年级+','  like ',2019,'

年级设置参数时：

select * from table where ','+年级+','  like ',${年级},'