创建数据库、表、表约束以及删除约束

USE master
GO
IF EXISTS (SELECT * FROM sysdatabases WHERE name=‘stuDB‘)
    DROP DATABASE stuDB
CREATE DATABASE stuDB
ON PRIMARY
(
/*--数据文件的具体描述*/
NAME=‘stuDB_data‘,
FILENAME=‘D:\MyCreateDBTest\stuDB_data.mdf‘,
SIZE=3mb,
MAXSIZE=100mb,
FILEGROWTH=15%
)
LOG ON
(
/*日记文件的具体描述*/
NAME=‘stuDB_log‘,
FILENAME=‘D:\MyCreateDBTest\stuDB_log.ldf‘,
SIZE=1mb,
FILEGROWTH=1mb
)
GO

USE stuDB
GO
IF EXISTS(SELECT * FROM sysobjects WHERE name=‘stuInfo‘)
    DROP TABLE stuInfo
CREATE TABLE stuInfo    /*创建学员信息表*/
(
stuID INT IDENTITY(1,1) PRIMARY KEY,  ----编号，标识列
stuName VARCHAR(20) NOT NULL,    ---学生姓名，非空（必填）
stuNo CHAR(6) NOT NULL,    ---学号，非空
stuAge INT NOT NULL,    ---年龄
stuID NUMERIC(18,0) ,    ---学生身份证号
stuAddress TEXT     ---学生住址
)
GO

IF EXISTS(SELECT * FROM sysobjects WHERE name=‘stuMarks‘)
    DROP TABLE stuMarks
CREATE TABLE stuMarks    /*创建学员成绩表*/
(
markID INT IDENTITY(1,1) PRIMARY KEY,
stuID INT NOT NULL,
mark FLOAT NOT NULL
)    
GO

ALTER TABLE stuMarks
    ADD CONSTRAINT FK_stuID
        FOREIGN KEY(stuID) REFERENCES stuInfo(stuID)
        
/*检查约束，要求年龄只能在15~40岁之间*/    
ALTER TABLE stuInfo
    ADD CONSTRAINT CK_stuAge CHECK(stuAge BETWEEN 15 AND 40)
    
/*默认约束，如果地址不详，则默认为“地址不详”*/
ALTER TABLE stuInfo
    ADD CONSTRAINT DF_stuAddress DEFAULT (‘地址不详‘) FOR stuAddress        
GO

ALTER TABLE stuInfo
    DROP CONSTRAINT FK_stuID