How to use String in mysql IN() function? -

i have varchar(255) field named "user_id" in database table in store comma separated user ids 234,235.

i have 1 inner query in query below 's' table alias:

(select group_concat(concat(first_name,' ',last_name)) users user_id in (s.user_id)) user_name 

now getting s.user_id value : '234,235' in result getting name of first user only. want both of users' name comma separated. (i want => ('234','235') or (234,235) works in in() function)

to use find_in_set() function not feasible query long.

storing ids in comma-separate string need reference bad design. it's better normalize data , store in ways database supports natively.

that said, need user id within string, 1 solution regular expression. this slow , think it's worth effort reorganize ids in separate table / column instead.

select group_concat(concat(first_name,' ',last_name))  users  s.user_id regexp concat('(^|,)', user_id, '($|,)') 

this matches id comma on either side or @ beginning or end of string.