使用double(6,2)
示例如下：

mysql> create table t(a double(6,2));
Query OK, 0 rows affected (0.10 sec)

mysql> insert t select 1234.56;
Query OK, 1 row affected (0.05 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> select * from t;
+---------+
| a       |
+---------+
| 1234.56 |
+---------+
1 row in set (0.00 sec)