Oracle's column operations (adding columns, modifying columns, deleting columns), including manipulating multiple columns

Add a column:

ALTER TABLE Emp4 Add test varchar2 (10);

To modify a column:

ALTER TABLE Emp4 Modify Test varchar2 (20);

Delete a column:

ALTER TABLE emp4 drop column test;

Here are a few places to note, first, add and modify the column is not required to add the keyword column, or will error ora-00905.

Second, to delete a single column, be sure to add column, and then remember that the deletion is not required to add the type.

Add multiple columns:

ALTER TABLE Emp4 Add (Test varchar2 (Ten), test2 number);

Modify multiple columns:

ALTER TABLE Emp4 Modify (test varchar2, Test2 varchar2 (20));

To delete multiple columns:

ALTER TABLE Emp4 drop (TEST,TEST2);

Strange phenomenon, in the column to add the keyword column, however, when you delete multiple columns, you cannot add the column keyword

Oracle's column operations (adding columns, modifying columns, deleting columns), including manipulating multiple columns