2015-12-01 SQL查询语句基础

1.查询全体学生的学号与姓名
select sno,sname
from student;
3.查询全体学生的详细信息
select *
from student;
4.查询全体学生的姓名及其出生年份
select sname,2004-sage
from student;
5.查询全体学生的姓名，出生年份和所在院系，要求用小写字母表示所有系名
select sname,'year of birth:',2004-sage,lower(sdept)
from student;
6.查询选修课程的学生学号，DISTINCT去掉重复行
select DISTINCT sno
from SC;

select sno
from SC;
等价于
select ALL sno
from SC;
7.查询计算机科学系全体学生的名单
select sname
from student
where sdept='cs';
8.查询所有年龄在20岁以下的学生姓名及其年龄
select sname,sage
from student
where sage<20;
9.查询考试成绩有不及格的学生的学号
select DISTINCT sno
from sc
where grade<60;
10.查询年龄在20~23岁（包括20岁和23岁）之间的学生的姓名，系别和年龄
select sname,sdept,sage
from student
where sage between 20 and 23;
11查询年龄不在20~23岁之间的学生的姓名，系别和年龄
select sname,sdept,sage
from student
where sage not between 20 and 23;
12.查询计算机科学系cs，数学系ma和信息系is学生的姓名和性别
select sname,ssex
from student
where sdept in('cs','ma','is');
13.查询不是计算机科学系cs，数学系ma和信息系is学生的姓名和性别
select sname,ssex
from student
where sdept not in('cs','ma','is');
14.查询学号为200215121的学生的详细情况
select *
from student
where sno like '200215121';
等价于
select *
from student
where sno='200215121';
15.查询所有姓刘的学生的姓名，学号和性别
select sname,sno,ssex
from student
where sname like '刘%';
16.查询所有不姓刘的学生的姓名，学号和性别
select sname,sno,ssex
from student
where sname not like '刘%';
17.查询姓欧阳且全名为3个汉字的学生的姓名
select sname
from student
where sname like '欧阳_';
19.查询DB_Design课程的课程号和学分
select cno,ccredit
from course
where cname like 'DB\_Design'ESCAPE'\';
ESCAPE'\'表示"\"为换码字符。这样匹配串中紧跟着"\"后面的字符"_"不再具有通配符的含义，转义为普通的"_"字符
20.查询以"DB_"开头，且倒数第3个字符为i的课程的详细情况
select *
from course
where cname like 'DB\_%i__'ESCAPE'\';
21.查询缺少成绩的学生的学号和相应的课程号
select sno,cno
from sc
where grade is null;
22.查询计算机科学系年龄在20岁以下的学生姓名
select sname
from student
where sdept='cs' and sage<20;
23.查询计算机科学系cs，数学系ma和信息系is学生的姓名和性别
select sname,ssex
from student
where sdept='cs' or sdept='ma' or sdept='is';
24.查询选修了3号课程的学生的学号及其成绩，查询结果按分数的降序排序
select sno,grade
from sc
where cno='3'
order by grade DESC;
25.查询全体学生情况，查询结果按所在系的系号升序排列，同一系的学生按年龄降序排列
select *
from student
order by sdept,sage DESC;
26.查询学生总人数
select COUNT(*)
from student;
27.查询选修了课程的学生人数
select COUNT(DISTINCT sno)
from sc;
28.计算1号课程的学生的平均成绩
select AVG(grade)
from sc
where cno='1';
29.查询选修1号课程的学生的最高分数
select MAX(grade)
from sc
where cno='1';
30.查询学生200215012选修课程的总学分数
select SUM(ccredit)
from sc,course
where sno='200215012' and sc.cno=course.cno;
31.求各个课程号及相应的选课人数
select cno,count(sno)
from sc
group by cno;
32.查询选修了3门以上课程的学生学号
select sno
from sc
group by sno
having count(*) >3;
33.查询每个学生及其选课情况
select student.*,sc.*
from student,sc
where student.sno=sc.sno;
35.查询每一门课的间接先修课
select first.cno=second.cpno
from course first,course second
where first.cpno =second.cno;
36.
select student.sno,sname,ssex,sage,sdept,cno,grade
from student left out join sc on (student.sno=sc.sno);
37.查询选修2号课程且成绩在90分以上的所有学生
select student.sno,sname
from student,sc
where student.sno=sc.sno and
sc.cno='2' and sc.grade>90;
38.查询每个学生的学号，姓名，选修的课程名及成绩
select student.sno,sname,cname,grade
from student,sc,course
where student.sno=sc.sno and sc.cno=course.cno;
39.查询与刘晨在同一系学习的学生
select sno,sname,sdept
from student
where sdept in
(select sdept
from student
where sname='刘晨');
等同于
select s1.sno,s1.sname,s1.sdept
from student s1,student s2
where s1.sdept=s2.sdept and
s2.sname='刘晨';
40.查询选修了课程名为“信息系统”的学生学号和姓名
select sno,sname
from student
where sno in
(select sno
from sc
where cno in
(select cno
from course
where cname='信息系统'
)
);
等价于
select student.sno,sname
from student,sc,course
where student.sno=sc.sno and
sc.cno=course.cno and
course.cname='信息系统';
41.找出每个学生超过他选修课程平均成绩的课程号
select sno,cno
from sc x
where grade>=(select AVG(grade)
from sc y
where y.sno=s.sno
);
42.查询其他系中比计算机科学系某一学生年龄小的学生姓名和年龄
select sname,sage
from student
where sage<ANY(select sage
from student
where sdept='cs'
)
and sdept <> 'cs';
43.查询其他系中比计算机科学系所有学生年龄都小的学生姓名及年龄
select sname,sage
from student
where sage < all
(select sage
from student
where sdept='cs'
)
and sdept <> 'cs';
44.查询所有选修了1号课程的学生姓名
select sname
from student
where EXISTS
(select *
from sc
where sno=student.sno and cno='1');
使用存在量词EXISTS后，若内层查询结果非空，则外层的WHERE子句返回真值，否则返回假值
45.查询没有选修1号课程的学生姓名
select sname
from student
where not exists
(select *
from sc
where sno=student.sno and cno='1');
46.查询选修了全部课程的学生姓名
select sname
from student
where not exists
(select *
from course
where not exists
(select *
from sc
where sno=student.sno
and cno=course.cno));
47.查询至少选修了学生200215122选修的全部课程的学生号码
select distinct sno
from sc scx
where not exists
(select *
from sc scy
where scy.sno='200215122' and
not exists
(select *
from sc scz where scz.sno=scx.sno and scz.cno=scy.cno));
48.查询计算机科学系的学生及年龄不大于19岁的学生
select *
from student
where sdept='cs'
union
select *
from student
where sage<=19;
union会自动去掉重复元组，而union all操作符可以保存重复元组
49.查询选修了课程1或者课程2的学生集合的并集
select sno
from sc
where cno='1'
union
select sno
from sc
where cno='2';
50.查询计算机科学系的学生与年龄不大于19岁的学生的交集
select *
from student
where sdept='cs'
intersect
select *
from student
where sage<=19;