Finding "words" separated by commas in a single column with the CONCAT_WS() function
WHERE FIND_IN_SET("LK123", CONCAT_WS(",", ...))


It does require the use of "comma" as the separator, and you cannot have commas in the strings.

https://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_find-in-set

Or... FULLTEXT

ADD FULLTEXT(column1, column2)

WHERE MATCH(column1, column2) AGAINST("+KL123 +OTHER123" IN BOOLEAN MODE)


Yes, your app will need to construct this syntax.