Article directory
If you want to use mysql normally, you must ensure that there are these three files
- mysql is the client of the database
- mysqld is the server side of the database
(mysql is the mode of server and client)
start mysql
(Start the mysql server, that is, mysqld)
systemctl start mysql
mysql is a network layer service and an application layer process
log in to mysql
View version
When you first log in, mysql has only one root account
1. MySQL environment installation and basic understanding
Modify the port number
The default port number is 3306, you can modify the port number
vim /etc/my.cnf
Then restart mysql
systemctl restart mysqld
connect to the server
mysql -h 127.0.0.1 -P 3306 -u root -p
server, database, table relationship
- create database
Entering the database
does not specify the ip by default, and if the port is not specified, it is local by default. The essence of these steps just now when 3306
creates the database
is: I build a sql on my client, and the sql statement is handed over to us through the network or inter-process communication server process. The server process received my sql command, and then there must be a corresponding system call inside his process to help us create this directory, which is called a database
build table
If you want to create a table under the database, you must first enter the database
to use the XXX database
use xxx
Check which database you are in now
select database（）；
Create a table below.
What is the essence of building a database on Linux? In mysq, creating a database create database XXX essentially creates a directory under lnux! What is the essence of
building a table on Linux? ? In mysgl In, the essence of creating a table is to create the corresponding file on Linux!
Insert information into the table
query the data in the table
Lecture 2_Library Operation
Basic functions of the database:
- More attribute operations on database and table structures
- For database and table structure, more data content operations
1. Create a database
create database 数据库名；
2. Create a database case
1. Create a database
3. Specify the character set and checksum
The impact of validation rules on the database
Setting the encoding and verification rules of the database, who will essentially affect who? In fact, it affects the corresponding internal tables in the database, and the corresponding encoding and verification rules
(1) Create a database gc_db, use utf8_ general_ ci [case-insensitive] for verification rules
(2) create a database bin_db, use utf8_ bin [case-sensitive] for verification rules
Case-insensitive query and results:
(3) Choose to use the gc_db database
(4) Create a table structure in the database
create table person(name varchar(20))；
Check the attribute column of a table:
desc person;
Insert some properties:
insert into person values('a');
insert into person values('A');
insert into person values('b');
insert into person values('B');
Case-insensitive query and result:
name is a
select * from person
select * from person where name='a';
Case-sensitive queries and results
Use the bin_db database, go through the above steps again, create tables, insert attributes
Sort by name attribute
1. Case sensitive
default ascending sort
select * from person order by name;
2. Case insensitive
default ascending sort
delete database
The corresponding database folder is deleted, cascaded deletion, and all the data tables in it are deleted
drop database 数据库名；
Backup and restore – last
backup
mysqldump -P3306 -u root -p 密码 -B 数据库名 > 数据库备份存储的文件路径
Example: backup mytest library to file (exit connection)
mysqldump -P3306 -u root -p123456 -B mytest > D:/mytest.sql
find database
show database；
modify database
- The modification of the database mainly refers to modifying the character set of the database, and the verification rules
Example: Change the character set of mytest database to gbk
alter database gc_db charset=gbk;
alter database gc_db charset set utf8mb4;
Currently does not support the modification of the database name, you can modify the table name
Lecture 3_Table operation
create table
create table XXX
create table users (
id int,
name varchar(20) comment '用户名',
password char(32) comment '密码是32位的md5值',
birthday date comment '生日'
) character set utf8 engine MyISAM;
Create table case:
view table
- View table structure
desc XXX；
- view table
select * from 表名;
modify table
In the actual development of the project, the structure of a certain table is often modified, such as field name, field size, field type, character set type of the table,
storage engine of the table, and so on. We also have requirements, adding fields, removing fields, and so on. Then we need to modify the table
to add/modify/delete the table
ALTER TABLE tablename ADD (column datatype [DEFAULT expr][,column
datatype]...);
ALTER TABLE tablename MODIfy (column datatype [DEFAULT expr][,column
datatype]...);
ALTER TABLE tablename DROP (column);
- Add a field in the users table to save the image path
mysql> alter table users add assets varchar(100) comment '图片路径' after birthday;
- Add two records in the users table
mysql> insert into users values(1,'a','b','1982-01-04'),(2,'b','c','1984-01-
04');
- Modify the name and change its length to 60
mysql> alter table users modify name varchar(60)；
- delete the password column
Note: Be careful when deleting a field, as the deleted field and its corresponding column data are gone
mysql> alter table users drop password;
- Modify the table name to employee
mysql> alter table users rename to employee;
- Change the name column to xingming
mysql> alter table employee change name xingming varchar(60); --新字段需要完整定义
delete table
drop table t1;
Mysql user management
create user
grammar:
create user '用户名'@'登陆主机/ip' identified by '密码';
case:
mysql> create user 'whb'@'localhost' identified by '12345678';
delete users
grammar:
drop user '用户名'@'主机名'
Example:
