SQL Server建库-建表-建约束----------------------------------------SQL Server建库-建表-建约束创建School数据库--------------------------------------
--创建School数据库之前：首先判断数据库是否存在，若存在则删除后再创建，若不存在则创建----exists关键字:括号里边能查询到数据则返回‘true’ 否则返回‘false’if exists(select * from sysdatabases where name = 'School')--exists返回‘true’则执行删除数据库操作--drop database School--exists返回‘false’则表明数据库不存在，直接创建create database Schoolon PRimary(--主数据库文件--name = 'School', --主数据文件逻辑名fileName = 'D:\project\School.mdf',--主数据文件物理逻辑名size = 5MB, --初始值大小maxsize = 100MB, --最大大小filegrowth = 15% --数据文件增长量)log on(--日志文件--name = 'School_log',filename = 'D:\project\School_log.ldf',size = 2MB,filegrowth = 1MB)go
----------------------------------------使用T-SQL创建employee数据库------------------------------------create database employeeon primary(--主要数据文件--name = 'employee1',filename = 'D:\project\employee1.mdf',size = 10MB,filegrowth = 10%),(--次要数据文件--name = 'employee2',filename = 'D:\project\employee2.ndf',size = 20MB,maxsize = 100MB,filegrowth = 1MB)log on(--第一个日志文件--name = 'employee_log1',filename = 'D:\project\employee_log1.ldf',size = 10MB,filegrowth = 1MB),(--第二个日志文件--name = 'employee_log2',filename = 'D:\project\employee_log2.ldf',size = 10MB,maxsize = 50MB,filegrowth = 1MB)
---------------------------------查询已存在的数据库信息---------------------------select * from sysdatabases
---------------------------------删除数据库------------------------------------drop database School
---------------------------------创建Student数据库表------------------------------1、选择操作的数据库--use Schoolgo
--判断表是否存在--if exists(select * from sysobjects where name = 'Student')drop table Student--2、创建表---create table Student( --具体的列名 数据类型 列的特征(是否为空)--StudentNo int identity(2,1) not null,LoginPwd nvarchar(20) not null,StudentName nvarchar(20) not null,Sex int not null,GradeId int not null,phone nvarchar(50) not null,BornDate datetime not null,Address nvarchar(255),Email nvarchar(50),IDENTITYcard varchar(18))go
---查看所有数据库对象(数据库表)---select * from sysobjects
drop table Student
----------------------创建subject课程表------------------------1、判断表是否存在；若存在则删除再创建，若不存在则直接创建--------if exists(select * from sysobjects where name = 'subject')drop table subject
use Schoolgo
---创建subject课程表--create table subject(SubjectNo int not null identity(1,1),SubjectName nvarchar(50),ClassHour int,GradeID int)
----------------------------------------创建Result成绩表------------------------1、判断表是否存在；若存在则删除再创建，若不存在则直接创建--------if exists(select * from sysobjects where name = 'Result')drop table Result
use Schoolgo
---创建Result成绩表--create table Result(StudentNo int not null,SubjectNo int not null,ExamDate Datetime not null,StudentResult int not null)
-----------------------------------------创建Grande年级表------------------------1、判断表是否存在；若存在则删除再创建，若不存在则直接创建--------if exists(select * from sysobjects where name = 'Grade')drop table Grade
use Schoolgo
---创建Grande年级表--create table Grade(GradeId int not null,GrandeName nvarchar(50))
-----------------------------------------T-SQL添加约束---------------------------给StudentNo添加主键约束---alter table Studentadd constraint pk_StuNo primary key(StudentNo)
--给身份证添加唯一约束--alter table Studentadd constraint uq_StuIdcard unique(IDENTITYcard)
---给地址address添加默认约束--alter table Studentadd constraint df_stuaddress default('地址不详') for Address
---删除地址address默认约束---alter table Studentdrop constraint df_stuaddress
----------出生日期添加检查约束--------alter table Studentadd constraint ck_stuBorndate check(Borndate > '1980-01-01')
---------与Grand（年级表）建立主外键关系--------
--1、添加Grade主键(操作Grade)---alter table Gradeadd constraint pk_graid primary key(GradeId)
--2、添加Grade外键(操作Student)--alter table Studentadd constraint fk_stuGradeID foreign key(GradeId) references Grade(GradeId)
-------------------给subject课程表添加约束-----------------------
----给subjectNo列添加主键约束------alter table subjectadd constraint pk_SubID primary key(SubjectNo)
------给课程名称subjectName添加非空约束；----------with nocheck：已经存在数据不通过check约束-------alter table subject with nocheckadd constraint ck_subName check(SubjectName is not null)
-----学时必须大于0-----alter table subject with nocheckadd constraint ck_ClassHour check(ClassHour > 0)
-----与Grade年级表添加主外键约束----alter table subject with nocheckadd constraint fk_GradeID foreign key(GradeID)references Grade(GradeID)
----------给result成绩表添加约束------------
-------添加多个约束---------alter table Resultadd constraint pk_No_subID_date primary key(StudentNo,SubjectNo,ExamDate),constraint df_examdate default(getdate()) for ExamDate,constraint ck_StudentResult check(StudentResult between 0 and 100),constraint fk_StuNo foreign key(StudentNo) references Student(StudentNo),constraint fk_subNo foreign key(SubjectNo) references Subject(SubjectNo)
--删除多个约束--alter table Resultdrop constraint pk_No_subID_date,fk_subNo,fk_StuNo,ck_StudentResult,df_examdate
--------更改列的数据类型----------alter table Resultalter column StudentResult int