Basic operation
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Preface
Since I have to learn database this semester, MySQL is particularly important, and I have been very interested in this aspect for a long time. I have been learning python crawlers before, and the data I have crawled have always wanted to be placed in the database. How can I not learn this aspect due to a number of reasons , So here, start recording your own learning today.
1. What is MySQL?
Baidu Encyclopedia explained this.
MySQL is an open source relational database management system (RDBMS) that uses the most commonly used database management language-Structured Query Language (SQL) for database management.
MySQL is open source, so anyone can download it under the General Public License and modify it according to individual needs.
MySQL has attracted much attention because of its speed, reliability and adaptability. Most people think that MySQL is the best choice for managing content when transactional processing is not required.
Two, installation steps
The installation process is not described here, please move to the network disk: https://pan.baidu.com/s/10qAbvv7we8zZnE_F2U_37Q
Extraction code: 94rc
Two, commonly used commands
1. Vignette
After the installation of MySQL is complete, open mysql
password and input is complete, and a crash occurs when you press Enter.
At the beginning, I didn't know the reason, and the environment variables were also well matched.
After checking a lot of information, I finally found a solution.
Windows+R Enter cmd to open the terminal.
Enter: mysql -u root -pEnter
to be resolved and enter MySQL.
2. Command usage
1. View all databases
show databases;
2. Create a database
named here with momo
create database momo;
3. Check it again.
Here is a newly created database momo.
4. Delete the database
drop database yingmo;
It can be seen that the database yingmo has been completely deleted, and the mosaic is my mistyped command.
5. Use the database momo
use momo;
6. Create a table, table name: student
7. Query the content in the table
Because the content in the table has not been created at this time, it is empty at this time.
8. Insert student information
insert into 表名(id,name,gender,grade) values ('1','lihua','M','95');
Continue to insert two more pieces of data.
insert into student(id,name,gender,grade) values ('2','lucy','F','85');
insert into student(id,name,gender,grade) values ('3','lina','F','90');
9. Modify the table name: student_grade
rename table 原表名 to 新表名;
At this time, the modification has been successful, and an error will occur if the original table name is entered again.
10. Delete a column of content in the table, here delete the gender column
alter table student_grade drop gender;
It has been deleted.
11. Modify the name length in the table (10->20)
alter table student_grade modify name varchar(20);
12. Modify the character set of the table
alter table student_grade character set gb2312;
13. Modify the information in the table,
modify all the scores to 90
update student_grade set grade=90;
All results will change at this time.
Modify the score of a single student, for example, modify the score with id 2 to 80.
update student_grade set grade=80 where id='2';
update student_grade set grade=80,name='libai' where id='2';
Several pieces of data have been modified.
14. Delete all records in the table
delete from student_grade;
或者
truncate table student_grade;
Table has been deleted
to sum up
Be regarded as the beginning of learning MySQL! The rivers and lakes are far away, meet at high places. One day you can become the person you want to be.