如何模糊检索,Reader属于文本类型

update CustomerList
set readers = readers + user_id
from customerlist a join customerlist 2 on a.id = b.id
where (这里面我就不会写了,请各位指教下)

我尝试过, Where a.readers not like in(select user_id from customerlist2) 这样写,不正确