MySQL multi table query

material ：
establish student and score surface

CREATE TABLE student (

id INT(10) NOT NULL UNIQUE PRIMARY KEY ,

name VARCHAR(20) NOT NULL ,

sex VARCHAR(4) ,

birth YEAR,

department VARCHAR(20) ,

address VARCHAR(50)

);

establish score surface .SQL The code is as follows ：

CREATE TABLE score (

id INT(10) NOT NULL UNIQUE PRIMARY KEY AUTO_INCREMENT ,

stu_id INT(10) NOT NULL ,

c_name VARCHAR(20) ,

grade INT(10)

);

2. by student Table and score Table add records

towards student The table inserts a record of INSERT The statement is as follows ：

INSERT INTO student VALUES( 901,‘ Boss Zhang ’, ‘ male ’,1985,‘ Department of Computer Science ’, ‘ Haidian District, Beijing ’);

INSERT INTO student VALUES( 902,‘ Zhang Laoer ’, ‘ male ’,1986,‘ Department of Chinese ’, ‘ Changping District, Beijing ’);

INSERT INTO student VALUES( 903,‘ Zhang San ’, ‘ Woman ’,1990,‘ Department of Chinese ’, ‘ Yongzhou City, Hunan Province ’);

INSERT INTO student VALUES( 904,‘ Li Si ’, ‘ male ’,1990,‘ English department ’, ‘ Fuxin City, Liaoning Province ’);

INSERT INTO student VALUES( 905,‘ Wang Wu ’, ‘ Woman ’,1991,‘ English department ’, ‘ Xiamen City, Fujian Province ’);

INSERT INTO student VALUES( 906,‘ Wang Liu ’, ‘ male ’,1988,‘ Department of Computer Science ’, ‘ Hengyang City, Hunan Province ’);

towards score The table inserts a record of INSERT The statement is as follows ：

INSERT INTO score VALUES(NULL,901, ‘ Computer ’,98);

INSERT INTO score VALUES(NULL,901, ‘ English ’, 80);

INSERT INTO score VALUES(NULL,902, ‘ Computer ’,65);

INSERT INTO score VALUES(NULL,902, ‘ chinese ’,88);

INSERT INTO score VALUES(NULL,903, ‘ chinese ’,95);

INSERT INTO score VALUES(NULL,904, ‘ Computer ’,70);

INSERT INTO score VALUES(NULL,904, ‘ English ’,92);

INSERT INTO score VALUES(NULL,905, ‘ English ’,94);

INSERT INTO score VALUES(NULL,906, ‘ Computer ’,90);

INSERT INTO score VALUES(NULL,906, ‘ English ’,85);

1. Inquire about student All the records of the table

2. Inquire about student Table No 2 Strip to 4 Bar record

3. from student Table to query the student numbers of all students （id）、 full name （name） And departments （department） Information about

4. from student The information of students in computer department and English department can be found in the table

5. from student Query in table 2010 Year age 18~22 Student information at age

6. from student How many people are there in each department

7. from score Query the highest score of each subject in the table

8. Inquire about Li Si's Examination subjects （c_name） And test scores （grade）

9. Query all the students' information and exam information in the way of connection

10. Calculate the total score of each student

11. Calculate the average score of each test subject

12. The computer score is lower than 95 Student information

**13.** Search for information about students who take both computer and English exams

14. Rank computer test scores from high to low

15. from student Table and score The student number can be found in the table , Then merge the query results

16. Check the names of students surnamed Zhang or Wang 、 Departments and examination subjects and results

17. All the inquiries are the names of the students in Hunan 、 Age 、 Departments and examination subjects and results