中国信保笔试题
填空题
1、关系代数以集合代数为基础运算，基本操作是并、差、笛卡儿积、投影和选择。规范化理论
中分解关系模式主要是消除多余的数据相关性。
2、数字签名常用公开密钥加密方法。发送者签名使用的密钥为发送者的公钥，
常用的加密算法有 Hash 签名、DSS 签名、RSA 签名。
3、Internet 实现组播，传输层协议为组播地址解析协议(MARS：Multicast Address Resolution Server)
4、完整性约束:
单个关系上的约束
not null
unique
check
参照完整性
断言
函数依赖
简答题
MVC 模式及其作用，列出至少两种目前流行的 MVC 组件。
六、数据库设计
1、建表
create table Company(companyName varchar2(30), id number(4) primary key);
create table EmployeeHired(id number(4), numberHired number(4),
FiscalYear number(4), FiscalQuarter number(4),
foreign key(id) references Company(id),
primary key(id, FiscalYear, FiscalQuarter));
2、插入数据
insert into Company values('Microsoft', 1);
insert into Company values('IBM', 2);
insert into Company values('HP', 3);
insert into Company values('Nortel', 4);
insert into EmployeeHired values(1, 1, 2007, 1);
insert into EmployeeHired values(1, 3, 2007, 3);
insert into EmployeeHired values(1, 3, 2008, 2);
insert into EmployeeHired values(2, 2, 2007, 2);
insert into EmployeeHired values(2, 4, 2007, 4);
insert into EmployeeHired values(2, 2, 2008, 1);
insert into EmployeeHired values(3, 5, 2008, 1);
insert into EmployeeHired values(3, 10, 2008, 2);
insert into EmployeeHired values(4, 3, 2008, 3);
insert into EmployeeHired values(4, 6, 2008, 4);
3、在表 Company 中加入一列 Address varchar2(40);
alter table Company
add Address varchar2(40);
4、将20xx年招员工人数超过3人的公司名称和总人数查出，按人数降序排列;
select companyName, sum(numberHired) as sum
from Company c, EmployeeHired e
where c.id = e.id and FiscalYear = 2008
group by e.id, companyName
having sum(numberHired) > 3
order by sum desc;
