作者：mmggqq
链接：https://zhuanlan.zhihu.com/p/32137597
来源：知乎
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学生表 Student
create table Student(SId varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10));
insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '1990-05-20' , '男');
insert into Student values('04' , '李云' , '1990-08-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-03-01' , '女');
insert into Student values('07' , '郑竹' , '1989-07-01' , '女');
insert into Student values('09' , '张三' , '2017-12-20' , '女');
insert into Student values('10' , '李四' , '2017-12-25' , '女');
insert into Student values('11' , '李四' , '2017-12-30' , '女');
insert into Student values('12' , '赵六' , '2017-01-01' , '女');
insert into Student values('13' , '孙七' , '2018-01-01' , '女');
科目表 Course
create table Course(CId varchar(10),Cname varchar(10),TId varchar(10))
insert into Course values('01' , '语文' , '02')
insert into Course values('02' , '数学' , '01')
insert into Course values('03' , '英语' , '03')
教师表 Teacher
create table Teacher(TId varchar(10),Tname varchar(10))
insert into Teacher values('01' , '张三')
insert into Teacher values('02' , '李四')
insert into Teacher values('03' , '王五')
成绩表 SC
create table SC(SId varchar(10),CId varchar(10),score decimal(18,1))
insert into SC values('01' , '01' , 80)
insert into SC values('01' , '02' , 90)
insert into SC values('01' , '03' , 99)
insert into SC values('02' , '01' , 70)
insert into SC values('02' , '02' , 60)
insert into SC values('02' , '03' , 80)
insert into SC values('03' , '01' , 80)
insert into SC values('03' , '02' , 80)
insert into SC values('03' , '03' , 80)
insert into SC values('04' , '01' , 50)
insert into SC values('04' , '02' , 30)
insert into SC values('04' , '03' , 20)
insert into SC values('05' , '01' , 76)
insert into SC values('05' , '02' , 87)
insert into SC values('06' , '01' , 31)
insert into SC values('06' , '03' , 34)
insert into SC values('07' , '02' , 89)
insert into SC values('07' , '03' , 98)
select * from sc;
select * from student;
select * from teacher;
select * from course;
--查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
select distinct *
from (select * from sc where cid = 01) c1
join (select * from sc where cid = 02) c2
on c1.sid = c2.sid
where c1.score > c2.score;
--查询同时存在" 01 "课程和" 02 "课程的情况
select *
from (select * from sc where cid = 01) c1
full outer join (select * from sc where cid = 02) c2
on c1.sid = c2.sid
where c1.cid is not null
and c2.cid is not null;
--查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩
select s.sid "学号", s.sname "学生姓名", temp."平均成绩"
from student s
right join (select sid, avg(score) "平均成绩"
from sc
group by sid
having avg(score) >= 60) temp
on s.sid = temp.sid;
--查询在 SC 表存在成绩的学生信息
select *
from student s
right join (select sid from sc group by sid) temp
on s.sid = temp.sid;
--查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )
select s.sname, s.sid, temp."选课总数", temp."总成绩"
from student s
left join (select sid, count(cid) "选课总数", sum(score) "总成绩"
from sc
group by sid) temp
on s.sid = temp.sid;
--查询「李」姓老师的数量
select *
from teacher
where tname like '李%'
--查询学过「张三」老师授课的同学的信息 （left join 中on and 对左表中字段做条件限制无意义，左表中所有数据依旧会被查出来，左表中的字段筛选必须在where中增加条件；对右表中字段做条件限制会对右表数据先做筛选再连接，结果不显示；join 中on and 对两边表中的字段做限制都会起作用。）
select *
from sc s
left join student t
on s.sid = t.sid
where s.cid = (select cid
from teacher t
left join course c
on t.tid = c.tid
where t.tname = '张三');
select student.*
from teacher, course, student, sc
where teacher.Tname = '张三'
and teacher.TId = course.TId
and course.CId = sc.CId
and sc.SId = student.SId;
--查询没有学全所有课程的同学的信息
select *
from student s
right join (select sid, count(cid)
from sc
group by sid
having count(cid) < 3) temp
on s.sid = temp.sid;
--查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息
select *
from student
where sid in (select sid
from sc
where cid in (select cid from sc where sid = 01)
group by sid);
--查询和" 01 "号的同学学习的课程完全相同的其他同学的信息 （case when then end可以用来行列转换）
select *
from (select sid "学号",
sum(case cid when '01' then score end) as "课程1",
sum(case cid when '02' then score end) as "课程2",
sum(case cid when '03' then score end) as "课程3"
from sc
group by sid)
where "课程1" is not null
and "课程2" is not null
and "课程3" is not null;
--查询没学过"张三"老师讲授的任一门课程的学生姓名 (对表连接不熟的情况下，尽量不用join，避免笛卡尔积。可使用子查询替代)
select *
from student
where sid not in
(select sid
from sc
where cid =
(select cid
from course
where tid = (select tid from teacher where tname = '张三')))
--查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩 (有些数据结果正确可能是漏洞暂时还没体现出来，取出正确的数据需要细心缜密的逻辑。)
select s1.sid, s2.sname, avg(s1.score)
from (select *
from sc
where sid in (select sid
from sc
where score < 60
group by sid
having count(cid) >= 2)) s1
left join student s2
on s1.sid = s2.sid
group by s1.sid,s2.sname;
--检索" 01 "课程分数小于 60，按分数降序排列的学生信息
select *
from student s1
right join (select *
from sc
where cid = 01
and score < 60) s2
on s1.sid = s2.sid
order by s2.score desc;
--按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩 (case when 不影响其他聚合函数的使用)
select sid,
sum(case cid when '01' then score end) "课程1",
sum(case cid when '02' then score end) "课程2",
sum(case cid when '03' then score end) "课程3",
avg(score) avg
from sc
group by sid
order by avg desc;
--查询各科成绩最高分、最低分和平均分：以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率及格为 >= 60，中等为：70 - 80，优良为：80 - 90，优秀为： >= 90要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
select * from sc;
select cid,
max(score) "最高分",
min(score) "最低分",
avg(score) "平均分",
sum(case when score >= 60 then 1 else 0 end) / count(score) "及格率",
sum(case when score >= 70 and score < 80 then 1 else 0 end) / count(score) "中等率",
sum(case when score >= 80 and score < 90 then 1 else 0 end) / count(score) "优良率",
sum(case when score >= 90 then 1 else 0 end) / count(*) "优秀率",
count(score) "选修人数"
from sc
group by cid
order by "选修人数" desc,cid asc;
--按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺 (rank函数用于分组排序，是跳跃排序，即：如果有两个第1名，则接下来就是第3，忽略第2的情况。)
select cid,
sid,
score,
RANK() over(partition by cid order by score desc) rank
from SC;
--按各科成绩进行排序，并显示排名， Score 重复时合并名次 (dense rank函数是连续排序，即：如果有两个第1名，接下来是第2，依次排列)
select cid,sid,score,DENSE_RANK() over(partition by cid order by score desc)排名 from SC;
--查询学生的总成绩，并进行排名，总分重复时保留名次空缺
select sid 学号,sum(score)总分 ,rank() over(order by sum(score) desc) 排名 from sc group by sid;
select sid 学号,总成绩,RANK() over(order by 总成绩 desc)排名 from(select Sid,SUM(score)总成绩 from SC group by Sid);
--查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
select sid,sum(score),dense_rank() over(order by sum(score) desc) 排名 from sc group by sid ;
--统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比
select * from sc;
select cid,
sum(case when score >= 85 then 1 else 0 end) "100-85",
sum(case when score >= 70 and score < 85 then 1 else 0 end) "70-80",
sum(case when score >= 60 and score < 70 then 1 else 0 end) "60-70",
sum(case when score < 60 then 1 else 0 end) "60-0"
from sc
group by cid;
--查询各科成绩前三名的记录
select sid, cid,score,a
from (select sid, cid, score,dense_rank() over(partition by cid order by score desc) a
from sc)
where a <= 3;
-- 查询每门课程被选修的学生数
select cid,count(sid) 学生人数 from sc group by cid;
-- 查询出只选修两门课程的学生学号和姓名
select c.sid,s.sname from (select sid,count(cid) a from sc group by sid) c left join student s on c.sid=s.sid where c.a=2;
--查询男生、女生人数
select ssex,count(sid) from student group by ssex;
--查询名字中含有「风」字的学生信息
select * from student where sname like '%风%';
--查询同名同性学生名单，并统计同名人数
select * from (select sname,ssex,count(*) c from student group by sname,ssex) where c>1;
--查询 1990 年出生的学生名单 (extract 用于提取时间的部分，如：年、月、日、时、分、秒)
select * from student where sage>=to_date('1990-01-01','yyyy-mm-dd') and sage<to_date('1991-01-01','yyyy-mm-dd');
select * from student where extract(year from sage)=1990;
-- 查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
select cid,avg(score) a from sc group by cid order by a desc,cid asc;
--查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩
select a.sid,a.avg,b.sname from (select sid,avg(score) avg from sc group by sid having avg(score)>=85) a left join student b on a.sid=b.sid ;
-- 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
select a.sid,a.score,b.sname from sc a left join student b on a.sid=b.sid where a.cid=(select cid from course where cname='数学')
--查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）
select * from student s
left join (select sid,
sum(case cid when '01' then score else null end) as "01",
sum(case cid when '02' then score else null end) "02",
sum(case cid when '03' then score else null end) "03"
from sc group by sid) a
on s.sid=a.sid;
--查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数
select s.sname, c.cname, sc.score
from sc
left join student s
on sc.sid = s.sid
left join course c
on sc.cid = c.cid
where sc.score > 70
--查询不及格的课程
select * from sc where score<60;
-- 查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名
select c.sid,s.sname from sc c left join student s on c.sid=s.sid where c.cid=01 and c.score>80;
--求每门课程的学生人数
select cid,count(*) from sc group by cid
--成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩 (rownum给已有结果进行编号，属于虚拟编号，可以用于查询第一条数据。在这个例子中因为select子句执行在order by之前，所以需要用到子查询。)
select sid, cid, score, rownum
from (select sid, cid, score
from sc
where cid =
(select cid
from course
where tid = (select tid from teacher where tname = '张三'))
order by score desc)
where rownum = 1
--成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
select *
from (select sid, cid, score, (rank() over(order by score desc)) r
from sc
where cid =
(select cid
from course
where tid = (select tid from teacher where tname = '张三')))
where r = 1
-- 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
-- 查询每门功成绩最好的前两名
select *
from (select sid, cid, rank() over(partition by cid order by score desc) r
from sc)
where r = 1
or r = 2
-- 统计每门课程的学生选修人数（超过 5 人的课程才统计）。
select cid,count(sid) from sc group by cid having count(sid)>5
-- 检索至少选修两门课程的学生学号
select sid,count(cid) from sc group by sid having count(cid)>=2
--查询选修了全部课程的学生信息
select sid, count(cid)
from sc
group by sid
having count(cid) = (select count(cid) from course)
--查询各学生的年龄，只按年份来算
select sid 学号,extract(year from sysdate)-extract(year from sage) 年龄 from student;
--查询本周过生日的学生
select
--查询下周过生日的学生
-- 查询本月过生日的学生
-- 查询下月过生日的学生
来源：https://www.cnblogs.com/ningqd/p/11017310.html