Oracle Column Operations (adding columns, modifying columns, and deleting columns), including operations on multiple columns

Add a column:

Alter table emp4 add Test varchar2 (10 );

Modify a column:

Alter table emp4 modify test varchar2 (20 );

Delete a column:

Alter table emp4 drop column test;

 

Here pay attention to a few places, first, add and modify the column is not need to add the keyword column, otherwise it will report an error ora-00905.

Second, if you delete a single column, you must add column. Remember that you do not need to add the column type to delete the column.

 

Add multiple columns:

Alter table emp4 add (test varchar2 (10), Test2 number );

Modify multiple columns:

Alter table emp4 modify (test varchar2 (20), Test2 varchar2 (20 ));

Delete multiple columns:

Alter table emp4 drop (test, Test2 );

It is strange that the keyword column must be added to a single column. However, when you delete multiple columns, the column keyword cannot be added.