SQL数据库的基础知识及使用！

--指向当前要使用的数据库
use master
go
--判断当前数据库是否存在
if exists (select * from sysdatabases where name='SMDB')
drop database SMDB --删除数据库
go
--创建数据库
create database SMDB
on primary
(
--数据库文件的逻辑名
    name='SMDB_data',
    --数据库物理文件名（绝对路径）
    filename='D:\DB\SMDB_data.mdf',
    --数据库文件初始大小
    size=10MB,
    --数据文件增长量
    filegrowth=1MB
)
--创建日志文件
log on
(
    name='SMDB_log',
    filename='D:\DB\SMDB_log.ldf',
    size=2MB,
    filegrowth=1MB
)
go
--创建学员信息数据表
use SMDB
go
if exists (select * from sysobjects where name='Students')
drop table Students
go
create table Students
(
    StudentId int identity(100000,1) ,
    StudentName varchar(20) not null,
    Gender char(2)  not null,
    Birthday smalldatetime  not null,
    StudentIdNo numeric(18,0) not null,--身份证号
    StuImage text null,--学员照片
    Age int not null,
    PhoneNumber varchar(50),
    StudentAddress varchar(500),
    ClassId int not null  --班级外键
)
go
--创建班级表
if exists(select * from sysobjects where name='StudentClass')
drop table StudentClass
go
create table StudentClass
(
ClassId int primary key,
    ClassName varchar(20) not null
)
go
--创建成绩表
if exists(select * from sysobjects where name='ScoreList')
drop table ScoreList
go
create table ScoreList
(
    Id int identity(1,1) primary key,
    StudentId int not null,
    CSharp int null,
    SQLServerDB int null,
    UpdateTime smalldatetime not null
)
go
--创建管理员用户表
if exists(select * from sysobjects where name='Admins')
drop table Admins
create table Admins
(
LoginId int identity(1000,1) primary key,
    LoginPwd varchar(20) not null,
    AdminName varchar(20) not null
)
go
--创建数据表的各种约束
use SMDB
go
--创建“主键”约束primary key
if exists(select * from sysobjects where name='pk_StudentId')
alter table Students drop constraint pk_StudentId




alter table Students
add constraint pk_StudentId primary key (StudentId)




--创建检查约束check
if exists(select * from sysobjects where name='ck_Age')
alter table Students drop constraint ck_Age
alter table Students
add constraint ck_Age check (Age between 18 and 35)




--创建唯一约束unique
if exists(select * from sysobjects where name='uq_StudentIdNo')
alter table Students drop constraint uq_StudentIdNo
alter table Students
add constraint uq_StudentIdNo unique (StudentIdNo)








--创建身份证的长度检查约束
if exists(select * from sysobjects where name='ck_StudentIdNo')
alter table Students drop constraint ck_StudentIdNo
alter table Students
add constraint ck_StudentIdNo check (len(StudentIdNo)=18)




--创建默认约束 
if exists(select * from sysobjects where name='df_StudentAddress')
alter table Students drop constraint df_StudentAddress
alter table Students 
add constraint df_StudentAddress default ('地址不详' ) for StudentAddress




if exists(select * from sysobjects where name='df_UpdateTime')
alter table ScoreList drop constraint df_UpdateTime
alter table ScoreList 
add constraint df_UpdateTime default (getdate() ) for UpdateTime








--创建外键约束
if exists(select * from sysobjects where name='fk_classId')
alter table Students drop constraint fk_classId
alter table Students
add constraint fk_classId foreign key (ClassId) references StudentClass(ClassId)




if exists(select * from sysobjects where name='fk_StudentId')
alter table ScoreList drop constraint fk_StudentId
alter table ScoreList
add constraint fk_StudentId foreign key(StudentId) references Students(StudentId)

use SMDB
go




--插入班级数据
insert into StudentClass(ClassId,ClassName) values(1,'网监1区')
insert into StudentClass(ClassId,ClassName) values(2,'网监2区')
insert into StudentClass(ClassId,ClassName) values(3,'信息安全')
insert into StudentClass(ClassId,ClassName) values(4,'计算机科学与技术')




--插入学员信息
insert into Students (StudentName,Gender,Birthday,Age,StudentIdNo,PhoneNumber,StudentAddress,ClassId)
         values('苏家辉','男','1989-08-07',22,120223198908071111,'022-22222222','天津市南开区红磡公寓5-5-102',1),
 ('小美女','女','1989-05-06',22,120223198905062426,'022-33333333','天津市河北区王串场58号',2),
         ('小帅哥','男','1990-02-07',21,120223199002078915,'022-44444444','天津市红桥区丁字沽曙光路79号',4)






--插入成绩信息
insert into ScoreList (StudentId,CSharp,SQLServerDB)values(100000,60,78),(100001,55,88),(100002,90,58)




--插入管理员信息
insert into Admins (LoginPwd,AdminName) values(123456,'杨家贵')
insert into Admins (LoginPwd,AdminName) values(123456,'陈皮')
insert into Admins (LoginPwd,AdminName) values(123456,'刘懿蝉')