Oracle tables, fields, column operations ____oracle

1, Add the field Alter table Student Add age number (5);  2, modify the field ALTER TABLE student Modify age number (10);  ALTER TABLE table2 Rename column result to RESULT2;  3. Delete field Alter table student Drop column age;   4, empty the table student data Truncate; The data is normally deleted and if the deletion is found to be incorrect, it can be rolled back by rollback.  If you use a truncated table, all data is not recoverable. So fast (see Oracle Architecture in more detail) 5, DROP table drop table student;    6, rename table Rename student to Student1;   Add a column: Alter TABLE A Add (Cfyjsnr varchar2 (20));    Modify column: ALTER TABLE A rename column Cfyjsnr to Cfjysnr;   Modify the column type: ALTER TABLE A modify CFYJ varchar (200); Delete database one column ALTER TABLE a drop column Cfyjsnr