Mysql根据时间查询日期的优化技巧

例如查询昨日新注册用户，写法有如下两种：

EXPLaiN
select * from chess_user u where DATE_FORMAT(u.reGISter_time,'%Y-%m-%d')='2018-01-25';
EXPLAIN
select * from chess_user u where u.register_time BETWEEN '2018-01-25 00:00:00' and '2018-01-25 23:59:59';