This query logic should work
where d = <cfqueryparam cfsqltype="cf_sql_varchar" value="#c#">
--- c is only element
or d like <cfqueryparam cfsqltype="cf_sql_varchar" value="#c#,%">
--- c is first element
or d like <cfqueryparam cfsqltype="cf_sql_varchar" value="%,#c#,%">
--- c is in the middle somewere
or d like <cfqueryparam cfsqltype="cf_sql_varchar" value="%,#c#">
--- c is last element