mysql中如何将字符串转化成日期？

Question

mysql应该不需要函数把字符串转化成日期吧，mysql应该是隐式转换。
mysql> desc tests;
+----------+--------------------+------+-----+---------+-------+
| Field    | Type               | Null | Key | Default | Extra |
+----------+--------------------+------+-----+---------+-------+
| users    | varchar(10) binary |      |     |         |       |
| passwd   | varchar(50) binary |      |     |         |       |
| datetime | date               | YES  |     | NULL    |       |
+----------+--------------------+------+-----+---------+-------+
3 rows in set (0.00 sec)mysql> insert into tests values ('wr',md5('wr'),'2002-05-28');mysql> select * from tests;
+--------+----------------------------------+------------+
| users  | passwd                           | datetime   |
+--------+----------------------------------+------------+
| webmin | 827ccb0eea8a706c4c34a16891f84e7b | NULL       |
| wr     | f3151d23f9c88ea74e0229bcdd321cde | 2002-05-28 |
+--------+----------------------------------+------------+
2 rows in set (0.02 sec)