1、创建测试表,create table test_cols(id number, id2 number, id3 number);
2、查看该表的字段名,select * from user_tab_columns t where table_name = upper('test_cols'),共有三列,
3、执行sql,删除一列ID2,alter table test_cols drop column id2,
4、再次查看该表的字段名,select * from user_tab_columns t where table_name = upper('test_cols'),只有两列,