|
|
Posted on 2007-08-22 23:17 郑成桥 阅读(920) 评论(0) 编辑 收藏
今天就随便的讲讲. 内连接... 假如 你有2张表.. 一个是学生表. 一个是成绩表. 你要查一个人的表的成绩. .你就要用到内连接 把2个表连接起来... 下面简单的教大家用 sql 来个内连接.~ 按照这步奏做..
1 create database zcq --建数据库
2
3  create table student /**//* 建一个学生表.. */
4(
5sno char(5),
6sname char(5),
7ssex char(2),
8sage int
9)
10/**//* 插入一些数据 */
11
12insert into student values ('001','小桥','男',18)
13insert into student values ('002','宝玉','女',20)
14insert into student values ('003','哈哈','男',17)
15insert into student values ('004','暗暗','男',16)
/**//* 再建一个成绩表 */
create table score
(
sno char(5),
cno int,
score int
)
insert into score values ('001','1',80)
insert into score values ('002','2',90)
insert into score values ('003','3',50)
insert into score values ('004','4',80)
insert into score values ('005','5',90)
insert into score values ('006','6',100)
1create table course
2(
3cno int,
4chame char(5)
5)
6
7
8
9insert into course values (1,'c')
10insert int o course values (2,'sql')
11insert into course values (3,'java')
12
查询他们最高分 最低分..
1
2--分数最高
3select top 1 cno,avg(score)
4from score
5group by cno
6--having avg(score)>0
7order by cno
8
9
10--分数最低
11select top 1 cno,avg(score)
12from score
13group by cno
14--having avg(score)>0
15order by cno desc
--查询一个叫宝玉的总分 和平均分
select sname , sum(score) as 总分,avg(score) as 平均分 from student inner join score on(student.sno=score.sno)
where sname like '%玉'
group by sname
--查询宝玉的sql成绩
select sname,score,sage,chame from score inner join student on(student.sno=score.sno) inner join course on(score.cno=course.cno)
where sname='宝玉' and chame='sql'
--年龄在17-20岁之间的女生
select *from score inner join student on(student.sno=score.sno) inner join course on(score.cno=course.cno)
where sage between 15 and 20 and ssex='女' and chame='sql'
___作者: 郑成桥
|