Linux MySQL Add, delete users, user rights, and MySQL maximum number of fields

1. Login:

Mysql-u username-p

Show all databases:

show databases;

Use a database:

Use DatabaseName;

Show all tables for a database:

Show tables;

Exit:

Quit

deleting databases and data tables

Mysql>drop database name;

Mysql>drop table Data Sheet name;

User-Related: View all users: SELECT DISTINCT CONCAT (' User: ', user, ' @ ', host, '; ') as query from Mysql.user; New User:

CREATE USER ‘dog‘@‘localhost‘IDENTIFIED BY ‘123456‘; 

Authorization for User: Format: Grant permission on database. * to [email protected] Login host identified by "password"; Demo sample: Grant all privileges on testdb.* to [em AIL protected] identified by ' 1234 '; then you need to run the Refresh Permission command: Flush privileges; Grant users partial permissions: Grant Select,update on testdb.* to [email protected] identified by ' 1234 '; Grant certain permissions to a user for all databases: Grant Select,delete,update,create,drop on * * to [email protected] "%" identified by "1234"; Delete User: Delete from user Where user= ' test ' and host= ' localhost '; then refresh permissions; Delete account and permissions: >drop user [email protected] '% ';

>drop user [email protected] localhost; Change the specified user password

Log in with Root:
Mysql-u root-p
To run the command:
Update Mysql.user set Password=password (' New password ') where user= "test" and host= "localhost";
Refresh permissions:
Flush privileges; 2. mysql Maximum number of fields

Type	Size	Description
Cahr (Length)	Length byte	Fixed-length field, 0~255 characters
VARCHAR (Length)	String length + 1 bytes or string length + 2 bytes	Variable Length field, 0~65 535 characters long
Tinytext	String length + 1 bytes	string with a maximum length of 255 characters
TEXT	String length + 2 bytes	string with a maximum length of 65 535 characters
Mediumint	String length + 3 bytes	string with a maximum length of 16 777 215 characters
Longtext	String length + 4 bytes	string with a maximum length of 4 294 967 295 characters
TINYINT (Length)	1 bytes	Range: -128~127, or 0~255 (unsigned)
SMALLINT (Length)	2 bytes	Range: 32 768~32 767, or 0~65 535 (unsigned)
Mediumint (Length)	3 bytes	Range:-8 388 608~8 388 607, or 0~16 777 215 (unsigned)
INT (Length)	4 bytes	Range:-2 147 483 648~2 147 483 647, or 0~4 294 967 295 (unsigned)
BIGINT (Length)	8 bytes	Range:-9 223 372 036 854 775 808~9 223 372 036 854 775 807, or 0~18 446 744 073 709 551 615 (unsigned)
FLOAT (Length, decimals)	4 bytes	A smaller number with a floating decimal point
DOUBLE (Length, decimals)	8 bytes	A larger number with a floating decimal point
DECIMAL (Length, decimals)	length+1 bytes or length+2 bytes	A double that is stored as a string that allows a fixed decimal point
DATE	3 bytes	Use YYYY-MM-DD format
Datetime	8 bytes	Using YYYY-MM-DD HH:MM:SS format
TIMESTAMP	4 bytes	in YYYYMMDDHHMMSS format; acceptable range terminated in 2037
Time	3 bytes	Use HH:MM:SS format
Enum	1 or 2 bytes	Shorthand for enumeration (enumeration), which means that each column can have one of several possible values
SET	1, 2, 3, 4, or 8 bytes	Like an enum, except that each column can have multiple possible values

Linux MySQL Add, delete users, user rights, and MySQL maximum number of fields