摘要：
高级查询： 1.连接查询 select*from info,nation where info.nation=nation.code join on select*from info join nation on info.nation=nation.code 2.联合查询 select code, 阅读全文
摘要：
创建表： create table Ceshi ( Uid varchar(50) primary key, Pwd varchar(50), Name varchar(50), Nation varchar(50), foreign key(Nation) reference Nation(Cod 阅读全文