SELECT a.Sno,a.Sname,Ssex,Sage,Sdept,cno grade FROM student a JOIN sc ON (a.Sno=sc.Sno);
Grade>=(SELECT AVG(grade) FROM sc scy WHERE scx.sno=scy.sno)AND
student.Sno=scx.Sno AND scx.Cno=course.Cno;
SELECT Student.Sno,Sname,Cname,Grade
FROM student,sc,course
WHERE student.Sno=sc.Sno AND sc.Cno=course.Cno;
SELECT Sname FROM student,sc Where student.Sno=sc.Sno AND sc.Cno='2';
SELECT scx.cno,Sname,cname,course.cno,grade FROM SC scx ,course,student WHERE
SELECT a.Sno,a.Sname,a.Sdept
FRom student a,student b
WHERE a.Sdept=b.Sdept and b.Sname="刘晨";
SELECT student.Sno,Sname,Cname FROM student,sc,course WHERE student.Sno=sc.Sno AND sc.Cno=course.Cno AND Cname="信息系统";
SELECT Sname ,Sage FROM student WHERE Sage<ANY(SELECT Sage FROM student WHERE Sdept='CS') AND Sdept<>'CS' ;
SELECT * FROM sc,student,course WHERE sc.Sno= student.Sno
AND sc.Cno=course.Cno;
SELECT DISTINCT Sno
From sc scx
WHERE NOT EXISTS(
SELECT * FROM sc scy
WHERE NOT E
#全称量词,不存在全程量词需要用存在量词转换,p=-(-p)
#离散数学,蕴含表达式p->q=-q V q
SELECT Sname FROM student
WHERE NOT EXISTS
(SELECT * FROM course WHERE NOT EXISTS
(SELECT * FROM sc ,student,course WHERE sc.Sno= student.Sno
AND sc.Cno=course.Cno
)
);
XISTS(
SELECT * FROM sc scz
WHERE scz.Sno=scx.sno AND scz.Cno =scy.Cno
)
);
#WHERE 语句不能加聚合函数,having可以使用聚合函数
SQL语句之多表查询
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转载自blog.csdn.net/p715306030/article/details/115363739
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