我们如何向现有 MySQL 表添加具有默认值的列？

Alter table table-name ADD (column-name datatype default data);

mysql> Alter table Student ADD(City Varchar(10) Default 'DELHI');

Query OK, 5 rows affected (0.33 sec)
Records: 5 Duplicates: 0 Warnings: 0

mysql> describe Student\g

+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| RollNO  | int(11)      | YES  |     | NULL    |       |
| Name    | varchar(20)  | YES  |     | NULL    |       |
| Class   | varchar(15)  | YES  |     | NULL    |       |
| Grade   | varchar(10)  | YES  |     | NULL    |       |
| Address | varchar(25)  | YES  |     | NULL    |       |
| Phone   | int(11)      | YES  |     | NULL    |       |
| Email   | varchar(20)  | YES  |     | NULL    |       |
| City    | varchar(10)  | YES  |     | DELHI   |       |
+---------+-------------+------+-----+---------+--------+

8 rows in set (0.04 sec)