目测一楼的 sql 不行
select user group by user 是可以，其它的字段必须是 aggregate function. select logintime 是不行的。另外 order 需要在 group 后面

1.分两次查询
SELECT user, count(*) AS cnt FROM userlog GROUP BY user ORDER BY cnt;
SELECT logintime FROM userlog WHERE user=? ORDER BY logintime;

2.利用 GROUP_CONCAT （ mysql 用得少，未实测，不保证书写正确）
SELECT user, count(*) AS cnt, GROUP_CONCAT(logintime SEPARATOR '\n' ORDER BY logintime) AS logintimes FROM userlog GROUP BY user ORDER BY cnt;