Oracle 如何修改列的数据类型

1.--#alter table fyt_ntj_table7   modify( dzdx varchar2(10));
2.--1.添加列add(newColumn varchar2(10))
3.  alter table fyt_ntj_table7 add(newColumn varchar2(10));
4.--2.赋值newColumn = dzdx
5.  update fyt_ntj_table7  set newColumn = dzdx;
6.  commit;
7.--3.删除原来的列和列的约束drop column dzdx
8.  alter table fyt_ntj_table7 drop column dzdx CASCADE   CONSTRAINTS;
9.--4.重命名newColumn to dzdx
10.  alter table fyt_ntj_table7 rename column newColumn to dzdx;