添加表中的列
ALTER TABLE major ADD majorRank number(3);
ALTER TABLE major ADD createDate DATE DEFAULT SYSDATE NOT NULL;
ALTER TABLE major ADD peopleNum number(4) CONSTRAINT ck_peopleNum CHECK(peopleNum > 30);

查看表中的列：
SELECT * FROM USER_TAB_COLS WHERE TABLE_NAME = 'MAJOR';

刪除列：
ALTER TABLE major DROP COLUMN majorRank;
ALTER TABLE major DROP (majorRank,peopleNum);

重命名列：
ALTER TABLE major RENAME COLUMN createDate TO foundDate;

設(shè)置列為UNUSED：
ALTER TABLE major SET UNUSED COLUMN foundDate;
ALTER TABLE major SET UNUSED (majorRank,CreateDate,peopleNum);

刪除表：
DROP TABLE major;

恢復被刪除的表
FLASHBACK TABLE major TO BEFORE DROP;

根據(jù)另外一個表創(chuàng)建表
CREATE TABLE newTable AS SELECT * FROM STUDENT;

添加表和列的注釋
COMMENT ON TABLE newTable is ‘Copy student struct’;

SELECT * FROM user_tab_comments where table_name = 'NEWTABLE';

COMMENT ON COLUMN newTable.studentID is 'Copy student.studentID';

SELECT * FROM user_col_comments where table_name = 'NEWTABLE';

刪除表：
DROP TABLE newTable;

清空回收站：
PURGE RECYCLEBIN;