drop table zmt_s_c;
drop table zmt_student;
drop table zmt_course;
create table zmt_student(
sno char(4) primary key not null,
sname nchar(10) not null,
sex char(1) check (sex= ‘M‘ or sex=‘F‘),//条件约束
age smallint check (age<=25 and age >=18)
);
insert into zmt_student values(‘1‘,‘张梦婷‘,‘F‘,22);
insert into zmt_student values(‘2‘,‘杨明珠‘,‘F‘,22);
insert into zmt_student values(‘3‘,‘崔雄‘,‘M‘,22);
insert into zmt_student values(‘4‘,‘马森‘,‘M‘,22);
insert into zmt_student values(‘5‘,‘曹真‘,‘M‘,22);
insert into zmt_student values(‘6‘,‘慕安峰‘,‘M‘,22);
create table zmt_course(
cno char(4) primary key not null,
cname char(10),
credit smallint not null check (credit>=0 and credit<=100)
);
insert into zmt_course values(‘1‘,‘数学‘,22);
insert into zmt_course values(‘2‘,‘英语‘,22);
insert into zmt_course values(‘3‘,‘语文‘,22);
create table zmt_student(
sno char(4) identity(1,1) primary key not null,//identity(1,1)：标识列， identity(a,b)，ab均为正整数，a表示开始数，b表示增幅，就像identity(1,1)意思就是该列自动增长，由1开始每次增加是1，
sname nchar(10) not null,
sex char(1) check (sex= ‘M‘ or sex=‘F‘),
age smallint check (age<=25 and age >=18)
);
create table zmt_course(
cno char(4) identity(1,1) primary key not null,
cname char(10),
credit smallint not null check (credit>=0 and credit<=100)
);
create table zmt_s_c(
sno char(4),
cno char(4),
grade smallint check(grade>=0 and grade <=100),
constraint zmt_s_c_sno_fk foreign key(sno) references zmt_student(sno), //外键约束
constraint zmt_s_c_cno_fk foreign key(cno) references zmt_course(cno)
);
insert into zmt_s_c values(‘1‘,‘2‘,80);
insert into zmt_s_c values(‘1‘,‘1‘,77);
insert into zmt_s_c values(‘1‘,‘3‘,90);
--1.查询性别不是男的学生的姓名
select sname from zmt_student where sex!=‘M‘;
--2.查询性别是男的 年龄大于20的学生姓名
select sname from zmt_student where sex=‘M‘ and age>20;
--3.按照课程号降序排列 课程名升序排序 查询出结果集
select * from zmt_course order by cno desc,cname asc;
--4.在S_C表中，查询学号是1的学生 一共修了几门课程
select count(cno) from zmt_s_c where sno=‘1‘;