alter table tbname drop column colname;
如:
SQL> desc a1;
 名称                                                  空值?    类型
 ----------------------------------------------------- -------- --------------
 BBB                                                   NOT NULL VARCHAR2(10)
 CCC                                                            VARCHAR2(20)SQL> alter table a1 drop column ccc;表已更改。SQL> desc a1;
 名称                                                  空值?    类型
 ----------------------------------------------------- -------- --------------
 BBB                                                   NOT NULL VARCHAR2(10)SQL>