自連接

查詢與“數(shù)據(jù)結構”學分相同的課程的課程名和學分

SELECT C2.Cname,C1.Credit

FROM Course C1 JOIN Course C2

ON C1.credit=C2.credit

where C2.Cname=‘數(shù)據(jù)結構‘

and C2.Cname!=‘數(shù)據(jù)結構‘

外連接

查詢學生的選課情況，包括選了課程的學生和沒有選課程的學生

SELECT Student.Sno,Sname,Cno,Grade

FROM Student left join SC

on Student.Sno=SC.Sno

或

SELECT STUDENT.sno,Sname,Cno,Grade

FROM SC right join Student

on Student.Sno=SC.Sno

查詢哪些課程沒有人選，列出其課程名

SELECT Cname from Couse C left join SC

on C.Cno=SC.Cno

where SC.cno IS null

with ties

select top 3 with ties Sname,Sdept,Grade

from Student S join SC on S.Sno=SC.Sno

where Cname=‘Java‘

Order by Grade DESC

select sno,sname,sdept from Student

where sdept in (

select sdept from Student where sname=‘劉晨‘

select S2.Sname from Student S1 Join Student S2

on S1.Sdept=S2.sdept

where S1.Sname=‘l劉晨‘

總結

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