--1統(tǒng)計每個班級有多少人 select grade,count(sname) from ze_student group by grade;
--2、2007級的各學生的平均成績 沒有成績的為0； select a.sname,(select avg(nvl(b.score,0)) from ze_score b where b.s#=a.s#) from ze_student a where grade=2007;
--3 每科 平均成績和最高成績 最低成績 2007級 保留2位小數(shù)點 四舍五入 select b.c#,avg(b.score),max(b.score),min(nvl(b.score,0)) from ze_student a,ze_score b where b.s# = a.s# and a.grade =2007 group by b.c#;
--4 給2007級 數(shù)學加5分 update ze_score set score=nvl(score,0)+5 where s# in (select s# from ze_student where grade=2007) and c# =(select c# from ze_course where cname='數(shù)學');
--5 90分以上的為優(yōu)秀 90到85為良好，60分 不及格 各人平均成績 select s#, c, case when c>=90 then '優(yōu)秀' when c90 and c>=60 then '及格' else '不及格' end as jige from (select s#,avg(nvl(score,0)) as c from ze_score group by s# ) order by jige desc;
--6 求同月出生的 人數(shù) select to_char(difdate,'mm') as 月份,count(s#) as 出生人數(shù) from ze_student group by to_char(difdate,'mm');
--7 各科的及格率和平均成績 截取 保留2位 --及格率 select c#,avg(nvl(score,0))as 平均成績,sum(nvl(score,0))as 總成績, count(s#) as 各科人數(shù), trunc(sum( case when nvl(score,0)>60 then '1' else '0' end)/count(s#),2) as 及格率 from ze_score group by c#;
--每人的及格率 select s#, avg(nvl(score,0))as 平均成績,sum(nvl(score,0))as 總成績, count(c#) as 總科目, sum( case when nvl(score,0)>60 then 1 else 0 end )/count(c#) as 及格率 from ze_score group by s#;
--8刪除 姓名是張三 的大學語文 成績 select * from ze_score where s# in (select s# from ze_student where sname in '張三') and c#=(select c# from ze_course where cname ='大學語文');
--9 將數(shù)學替換成高等數(shù)學 update ze_course set cname='高等數(shù)學'where cname like '%數(shù)學%';
--10 格式化 ，顯示 將學號修改成S開頭 不足12位補0； --查詢 select concat('S',lpad(s#,11,0)) as s# from ze_score ; select concat('S',lpad(s#,11,0)) as s# from ze_student ;
--格式化 update ze_score set s#= concat('S',lpad(s#,9,0)); update ze_student set s#= concat('S',lpad(s#,9,0));
四個足球隊
select a.name,b.name from qiu a,qiu b where a.nameb.name;
