Database Experiment 3: data query

Experiment three Data query experiment guidance

（ Simple queries and complex queries ）

1． The experiment purpose

（1） Yes, experiment 1 、 Experiment 2 has been built student 、course 、sc Query table .

（2） Fully experience SQL Structured query function of language , Let students fully understand SQL The flexibility of language , Powerful .

2． Experimental content

（1） Based on Experiment 1 and Experiment 2 , Query the database , Fully experience SQL The power of language . Simple query ： Simple single table query with selection and projection .、 contain between、is null Single table query with equal conditions . Single table query with grouping and sorting 、 Simple multi table query with join conditions .

（2） nested queries ： Use In Nested query of phrases 、 Use Exists Nested query of phrases 、 Multi table query using set operation .

3． The experimental requirements

(1) Check the student number and name of all students .

SELECT sno,sname FROM student;

(2) Check the detailed records of all students .

SELECT * FROM student;

(3) Check all students' names and year of birth .

SELECT sname,sage FROM student;

(4) Query the student number of the students who have taken the course .

SELECT sno from sc;

(5) Check the names of students in the computer department .

SELECT sname from student where sdept=' Department of accounting ';

(6) The age of inquiry is 20 Student number and age of computer students under years old .

SELECT sno,sage from student where sdept=' Department of accounting ' AND sage<20;

(7) The age of inquiry is 20—22 The student number of a 12-year-old student .

SELECT sno FROM student WHERE sage BETWEEN 20 AND 22;

(8) Query information system 、 Information for students of computer department and foreign language department .

SELECT * FROM student WHERE sdept IN(' Department of accounting ',' Department of telecommunications ',' Department of foreign languages ');

(9) Check the last name “ Wu ” Information about our students .

SELECT * FROM student where sname LIKE ' Wu %';

(10) Check the elective course 3 Student number and grades of students in course No , The results are arranged in descending order of scores .

SELECT sno,grade FROM sc WHERE cno='3' ORDER BY grade DESC; 

(11) Check the total number of students .

SELECT COUNT(*) FROM student;

(12) Check options 1 The highest score of students in course No .

SELECT MAX(grade) FROM sc where cno='1';

(13) Check the elective course 3 Student number of students with more than courses .

SELECT sno FROM sc HAVING COUNT(sno) > 3;

(14) Inquire about each student and their elective courses .

SELECT

	student.sno,
	
	sname,
	
	course.cno,
	
	course.cname,
	
	grade

FROM

	student,
	
	course,
	
	sc

WHERE

	student.sno = sc.sno
	
	AND sc.cno = course.cno;

(15) Check options 2 Course No. and the score is 90 All students with scores above .

SELECT

	student.sno,
	
	sname,
	
	grade,
	
	cno

FROM

	student,
	
	sc

WHERE

	student.sno = sc.sno
	
	AND cno='2'
	
	AND grade>90;

(16) Check the student number of each student 、 full name 、 Course name and grade .

SELECT

	student.sno,
	
	sname,
	
	cno,
	
	grade

FROM

	student,

	sc

WHERE

	student.sno = sc.sno;

(17) Query and “ Zhang San ” Students in the same department .

SELECT

	sno,
	
	sname,
	
	sdept

FROM

	student

WHERE

	sdept = (
	
	SELECT
	
	sdept

FROM

	student

WHERE

	sname = ' Qi Junbao '

);

(18) Query the elective course named “ database ” Student ID and name of .

SELECT

	student.sno,

	sname

FROM

	student,

	course,

	sc

WHERE

	student.sno = sc.sno
	
	AND course.cno = sc.cno
	
	AND course.cname = ' database ';

(19) There is no elective course 1 The name of the student in course No .

SELECT

	sname

FROM

	student

WHERE

	NOT EXISTS (
	
		SELECT
		
		*
		
		FROM
		
		sc
		
		WHERE
		
		student.sno = sc.sno
	
	AND sc.cno = '1'

);

(20) Query the names of students who have taken all courses .

SELECT

	sname
	
	FROM
	
	student

WHERE

	NOT EXISTS (
	
		SELECT
		
		*
		
		FROM
		
		course
		
		WHERE
		
		NOT EXISTS (
		
		SELECT
		
		*
		
		FROM
		
		sc
		
		WHERE
		
		student.sno = sc.sno
		
		AND sc.cno = course.cno
	
	)

);

Ask to write all the code of Experiment 3 ,
Be careful ：
1. All the code
2. The full width of the code
3. Regular format , Easy to read