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This article introduces the relevant knowledge of "what are the interview questions in the Java database?" in the operation of the actual case, many people will encounter such a dilemma, and then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Basic table structure:

Student (sno,sname,sage,ssex) student form

Course (cno,cname,tno) course schedule

Sc (sno,cno,score) score sheet

Teacher (tno,tname) teacher list

101, check the student numbers of all students whose grades in course 1 are higher than those in course 2

Select a.sno from

(select sno,score from sc where cno=1) a

(select sno,score from sc where cno=2) b

Where a.score > b.score and a.sno=b.sno

102, inquire about the student number and average score of the students whose grade point average is greater than 60

Select a.sno as "student number", avg (a.score) as "grade point average"

From

(select sno,score from sc) a

Group by sno having avg (a.score) > 60

103, check all students' student numbers, names, number of courses, and total grades.

Select a.sno as student number, b.sname as name

Number of courses selected by count (a.cno) as, total score of sum (a.score) as

From sc a, student b

Where a.sno = b.sno

Group by a.sno, b.sname

Or:

Selectstudent.sno as student number, student.sname as name

Number of courses selected by count (sc.cno) as, total score of sum (score) as

From student left Outer join sc on student.sno = sc.sno

Group by student.sno, sname

104, query the number of teachers surnamed "Zhang"

Selectcount (distinct (tname)) from teacher where tname like 'Zhang%'

Or:

Select tname as "name", count (distinct (tname)) as "number"

From teacher

Where tname like' Zhang%'

Group by tname

105, inquire about the student numbers and names of the students who have not taken the "Zhang San" teacher class.

Select student.sno,student.sname from student

Where sno not in (select distinct (sc.sno) from sc,course,teacher

Where sc.cno=course.cno and teacher.tno=course.tno and teacher.tname=' Zhang San')

106, query the student numbers and names of students who have taken both courses 1 and 2

Select sno, sname from student

Where sno in (select sno from sc where sc.cno = 1)

And sno in (select sno from sc where sc.cno = 2)

Or:

Selectc.sno, c.sname from

(select sno from sc where sc.cno = 1) a

(select sno from sc where sc.cno = 2) b

Student c

Where a.sno = b.sno and a.sno = c.sno

Or:

Select student.sno,student.sname from student,sc where student.sno=sc.sno and sc.cno=1

And exists (select * from sc as sc_2 where sc_2.sno=sc.sno and sc_2.cno=2)

107, look up the student numbers and names of all the students who have studied all the courses taught by teacher Li Si.

Select a.sno, a.sname from student a, sc b

Where a.sno = b.sno and b.cno in

(select c.cno from course c, teacher d where c.tno = d.tno and d.tname ='Li Si')

Or:

Select a.sno, a.sname from student a, sc b

(select c.cno from course c, teacher d where c.tno = d.tno and d.tname ='Li Si') e

Where a.sno = b.sno and b.cno = e.cno

108, check the student numbers and names of all students whose scores of course number 1 are higher than those of course number 2.

Select a.sno, a.sname from student a

(select sno, score from sc where cno = 1) b

(select sno, score from sc where cno = 2) c

Where b.score > c.score and b.sno = c.sno and a.sno = b.sno

109, check the student numbers and names of all students whose course scores are less than 60 points.

Select sno,sname from student

Where sno not in (select distinct sno from sc where score > 60)

110, query the student number and name of the student who has at least one course that is the same as that of the student with student number 1

Select distinct a.sno, a.sname

From student a, sc b

Where a.sno 1 and a.sno=b.sno and

B.cno in (select cno from sc where sno = 1)

Or:

Select s.sno,s.sname

From student s

(select sc.sno

From sc

Where sc.cno in (select sc1.cno from sc sc1 where sc1.sno=1) and sc.sno1

Group by sc.sno) R1

Where r1.sno=s.sno

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