修改table 的常用方法
添加列: alter table test_headers add col_test number;
修改列: alter table test_headers modify litem varchar2(40) not null;
刪除列: alter table test_lines drop column col_test;
重命名: alter table test_lines rename column col_test to col_test1;
添加主鍵: alter table test_hlines add constraint pk_test primary key(lineid);
添加外鍵: alter table test_lines add constraint fk_test foreign key (hid) reference test_headers(hid)
失效主鍵: alter table test_lines disable constraint pk_test;
失效外鍵: alter table test_lines disable constraint fk_test;
刪除主鍵: alter table test_lines drop constraint pk_test cascade;
刪除外鍵: alter table test_lines drop constraint fk_test