create database sqlserver use sqlserver --创建学校 create table school(id int primary key,name varchar(255) default '耶鲁大学') insert into school(id) values(1) select * from school --创建年级 use sqlserver truncate from table school/**truncate好像输出表了 待验证**/ delete from school create table class(id int constraint PK_class primary key,name varchar(255),sid int constraint FK_class_school foreign key(sid) references school(id)) select * from class insert into class values(1,'一班',1) --创建学生 create table student(id int,age int,cid int) alter table student alter column id int not null go alter table student add constraint PK_student primary key(id) go alter table student add check(age>0) go alter table student add constraint FK_student_class foreign key(cid) references class(id) go insert into student values(1,'Jack',23,1) ---联合查询 select school.name as 学校,class.name as 年级,student.name as 姓名,student.age 年龄 from student student left join class class on student.cid=class.id left join school school on class.sid=school.id ---把结果放在一行 select name as 信息 from school union all select name from class union all select name from student union all select convert(varchar(255),age) from student --查询表的信息 select * from sysobjects where id= object_id('school') select * from syscolumns --删除数据库 use master drop database sqlserver
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