摘要：
Fence RailsBurch, Kolstad, and SchrijversFarmer John is trying to erect a fence around part of his field. He has decided on the shape of the fence and has even already installed the posts, but he's having a problem with the rails. The local lumber store has dropped off boards of varying lengths; 阅读全文
摘要：
create table dept(dname char(7),loc char(4),id number(7) primary key);//建表desc dept;//查找表所具有的属性alter table dept add ddate date;//修改table表 dept 增加名为当ddate属性为date的属性组select * from dept;//选择所有表元素alter table dept drop column ddate;//删除dept 中在ddate列insert into dept (dname,loc,ddate)values('12',&# 阅读全文