数据库-数据表增删查改语法与实例

1.创建表的语法

Create Table Users
{
vUserName varchar(18) Not NULL,
vPassword varchar(20) Not NULL
}

2.学生表实例

2.1 创建带约束和主关键字的学生表

Create Table Student
{
Sno char(10) NOT NULL Constraint PK_stu_NO Primary Key,
Sname char(20) NOT NULL,
Ssex cahr(2) NOT NULL Constraint CK_Stu_Sex Check(Ssex in('男'，'女')),
Sage tinyint Constraint CK_Stu_Age Check(Sage between 1 and 80),
Tel char(15) NOT NULL
}

2.2 修改学生表

Alter Table Student Drop Constraint CK_Stu_Age

2.3 删除Sage列

Alter Table Student Drop Column Sage

2.4 添加列

Alter Table Student Add dBirth datetime

2.5 修改列字段大小

Alter Table Student Alter Column Smajor varchar(20)

2.6 删除先前的学生表

drop table student