SQL JOIN

 

stud:

Course:

stud_crs:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud inner join stud_crs on stud.sno = stud_crs.sno;

A intersects B:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud left outer join stud_crs on stud.sno = stud_crs.sno;

A:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud right outer join stud_crs on stud.sno = stud_crs.sno;

B:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud full outer join stud_crs on stud.sno = stud_crs.sno;

A unions B:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud left outer join stud_crs on stud.sno = stud_crs.sno
	where stud_crs.sno is null;

A - B:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud right outer join stud_crs on stud.sno = stud_crs.sno
	where stud.sno is null;

B - A:

 

select stud_crs.scno, stud.sno as 学号, stud.sname as 姓名, stud_crs.cno as 课程号, stud_crs.grade as 分数
	from stud full outer join stud_crs on stud.sno = stud_crs.sno
	where stud.sno is null or stud_crs.sno is null;

(A unions B) - (A intersects B):