1、修改table name：
mysql>alter table teacher rename tomaster;
Query OK, 0 rows affected (0.11 sec)
2、添加列：
mysql>alter table master add column salary double;
Query OK, 0 rows affected (0.61 sec)
Records: 0 Duplicates: 0 Warnings: 0
3、删除列：
mysql>alter table master drop column test;
Query OK, 0 rows affected (0.60 sec)
Records: 0 Duplicates: 0 Warnings: 0
4、修改列名：
mysql>alter table master change test tel int(13);
Query OK, 0 rows affected (0.08 sec)
Records: 0 Duplicates: 0 Warnings: 0
修改前列名：
修改后列名：
