mysql 中，如何把datetime字段，改成 date 字段，用什么函数？

Question

date_formate(fieldName, "%Y-%m-%d");

Answer 1

mysql> describe hello;
+-----------+----------+------+-----+---------+-------+
| Field     | Type     | Null | Key | Default | Extra |
+-----------+----------+------+-----+---------+-------+
| date      | date     | YES  |     | NULL    |       |
| date_time | datetime | YES  |     | NULL    |       |
+-----------+----------+------+-----+---------+-------+
2 rows in set (0.13 sec)mysql> select * from hello;
+------------+---------------------+
| date       | date_time           |
+------------+---------------------+
| 2004-01-07 | 2004-01-07 17:44:06 |
| NULL       | 2003-11-12 00:01:00 |
+------------+---------------------+
2 rows in set (0.05 sec)mysql> alter table hello change date_time date_time date;
Query OK, 2 rows affected (0.22 sec)
Records: 2  Duplicates: 0  Warnings: 0mysql> select * from hello;
+------------+------------+
| date       | date_time  |
+------------+------------+
| 2004-01-07 | 2004-01-07 |
| NULL       | 2003-11-12 |
+------------+------------+
2 rows in set (0.00 sec)mysql>