SELECT a.学号,a.姓名,b.课程号
from student a INNER JOIN score b
on a.学号=b.学号

SELECT a.学号,a.姓名,b.课程号
from student a LEFT JOIN score b
on a.学号=b.学号

-- 去除两张表的共同部分
SELECT a.学号,a.姓名,b.课程号
from student a LEFT JOIN score b
on a.学号=b.学号
where b.学号 is null

SELECT a.学号,a.姓名,b.课程号
FROM student a RIGHT JOIN score b
on a.学号=b.学号

-- 去除两张表共同部分
SELECT a.学号,a.姓名,b.课程号
FROM student a RIGHT JOIN score b
on a.学号=b.学号
where a.学号 is null

SELECT a.学号,a.姓名,count(b.课程号) 选课数,sum(b.成绩) 总成绩
FROM student a left join score b on a.学号=b.学号
group by a.学号

SELECT a.学号,a.姓名,avg(b.成绩) 平均成绩
FROM student a left join score b on a.学号=b.学号
group by a.学号
having avg(b.成绩)>85

select a.学号,a.姓名,c.课程号,c.课程名称
from student a
inner join score b on a.学号=b.学号
inner join course c om b.课程号=c.课程号

SELECT 学号,课程号,成绩,
(case when 成绩>=60 then '及格'when 成绩<60 then '不及格'else nullend) 是否及格
from score

SELECT 课程号,
sum(case when 成绩>=60 then 1 else 0 end) 及格人数,
sum(case when 成绩<60 then 1 else 0 end) 不及格人数
from score
group by 课程号

SELECT a.课程号,b.课程名称,
sum(case when 成绩<60 then 1 else 0 end) '<60',
sum(case when 成绩>=60 then 1 else 0 end) '60-70',
sum(case when 成绩>=70 then 1 else 0 end) '70-85',
sum(case when 成绩>=85 then 1 else 0 end) '85-100'
from score a RIGHT JOIN course b on a.课程号=b.课程号
group by a.课程号,b.课程名称

select matchid,playerfrom goalwhere teamid='ger';

SELECT id,stadium,team1,team2FROM game where  id=1012;

SELECT player,teamid,stadium,mdateFROM game JOIN goal ON (id=matchid)where teamid='ger';

select team1,team2,playerfrom game join goalon id=matchidwhere player like'mario%';

SELECT player, teamid, coach,gtimeFROM goal join eteam on teamid=idWHERE gtime<=10;

select mdate,teamnamefrom game join eteamon team1=eteam.idwhere coach='Fernando Santos';

select playerfrom goal join gameon id=matchidwhere stadium= 'National Stadium, Warsaw';

SELECT distinct playerFROM game JOIN goal ON matchid = id WHERE (team1='GER' and teamid=team2) or (team2='GER' and teamid=team1);

SELECT teamname, count(*)FROM eteam JOIN goal ON id=teamidgroup by teamname;

select stadium,count(*)from goal join gameon matchid=idgroup by stadium;

select a.id,a.mdate, count(b.player)from game as a inner join goal as b on a.id = b.matchid where (team1 = 'POL' or team2 = 'POL')group by a.id,a.mdate;

select a.id,a.mdate,count(player) from game as a inner join goal as b on a.id=b.matchid where b.teamid='GER' group by a.id,a.mdate;

SELECT a.mdate,a.team1,sum(CASE WHEN b.teamid=a.team1 THEN 1 ELSE 0 END) as score1,a.team2,sum(CASE WHEN b.teamid=a.team2 THEN 1 ELSE 0 END) as score2FROM game as a left JOIN goal as b ON  a.id=b.matchid group by a.id,a.mdate,a.team1,a.team2order by a.mdate,a.id,a.team1,a.team2;