SQL> create table lee(id number,name varchar2(100),score number,constraint pk_lee primary key(id));
Table created
SQL> desc lee
Name Type Nullable Default Comments
----- ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
SQL> alter table lee add createtime date;
Table altered
SQL> desc lee
Name Type Nullable Default Comments
---------- ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
CREATETIME DATE Y
SQL> alter table lee modify createtime nvarchar2(100);
Table altered
SQL> desc lee
Name Type Nullable Default Comments
---------- -------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
CREATETIME NVARCHAR2(100) Y
SQL> alter table lee rename column createtime to mytime;
Table altered
SQL> desc lee
Name Type Nullable Default Comments
------ -------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
MYTIME NVARCHAR2(100) Y
SQL> alter table lee modify mytime date;
Table altered
SQL> desc lee
Name Type Nullable Default Comments
------ ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
MYTIME DATE Y
SQL> desc lee
Name Type Nullable Default Comments
------ ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
MYTIME DATE Y
SQL> alter table lee rename column mytime to createtime;
Table altered
SQL> desc lee
Name Type Nullable Default Comments
---------- ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
CREATETIME DATE Y
SQL> alter table lee drop column createtime;
Table altered
SQL> desc lee
Name Type Nullable Default Comments
----- ------------- -------- ------- --------
ID NUMBER
NAME VARCHAR2(100) Y
SCORE NUMBER Y
SQL>