oracle new to add, delete columns, change column

- an increase:
ALTER the Add Table A (added columns VARCHAR2 (20 is));
- Modify columns:
ALTER Table A column the rename the old name to the new name;
- modified type column:
ALTER Modify Table A column name varchar (200 );
- delete a database
alter table A drop column column name;
- delete multiple columns of
the ALTER TABLE dROP table_name (column_name, ...);
- contrast two syntaxes can be seen, keyword cOLUMN is required when deleting a while you do not need when you delete multiple columns.
- Rename table
ALTER TABLE table RENAME TO new old table name;
- or
RENAME old table name TO new table name;