Some Oracle DDL operations

Oracle some DDL operation

Add fields

alter table tablename add (column datatype [default value][null/not null],….);

--  Add fields 
ALTER TABLE dept ADD(create_time date);
--  Add multiple fields 
ALTER TABLE dept ADD (
create_time date,
creator varchar2(100)
);

Delete field

alter table tablename drop (column);

ALTER TABLE dept DROP (create_time);

Add notes

--  Table annotation 
COMMENT ON TABLE dept IS ' Departmental table ';
--  Annotation fields 
COMMENT ON COLUMN dept.create_time IS ' Creation time ';