Operation of MySQL Library

Catalog

1. Create database

2. Create database case

3. Character set and verification rules  

4. Manipulating databases

         5. Backup and recovery  

6. Check the connection

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1. Create database

grammar

CREATE DATABASE [IF NOT EXISTS] db_name [create_specification [, create_specification] ...] 

create_specification: 
[DEFAULT] CHARACTER SET charset_name 
[DEFAULT] COLLATE collation_name

• Uppercase means keywords
• [] Optional.
• CHARACTER SET: Specifies the character set used by the database
• COLLATE: Specifies the verification rules for the database character set

                      

                          

2. Create database case

(1) Create a file called db1 The database of

• create database db1;
• When we create a database without specifying the character set and validation rules , The system uses the default character set ：utf8, The verification rule is ：utf8_general_ ci

(2)  Create a use utf8 Of the character set db2 database

• create database db2 charset=utf8;

(3) Create a use utf Character set , With proofreading rules db3 database

•  create database db3 charset=utf8 collate utf8_general_ci;

                 

3. Character set and verification rules  

(1) View the system default character set and verification rules

show variables like 'character_set_database'; 
show variables like 'collation_database';

                 

(2) View the character sets supported by the database  

• show charset;

• The character set mainly controls what language to use . such as utf8 You can use Chinese

                

(3) View the character set verification rules supported by the database

• show collation; 

•   The so-called verification rule is that when we store data, we store it normally , What kind of verification method should we use when taking ( Coding format ) Compare our data

                

(4) The impact of validation rules on the database  

① Case insensitive :  Create a database , Verification rules use utf8_ general_ ci[ Case insensitive ]

                 

② Case sensitive : Create a database , Verification rules use utf8_ bin[ Case sensitive ]

                 

③ The query

• Case insensitive queries and results : test1

• Case sensitive queries and results : test2

                 

④ Sorting results

• Case insensitive sorting and results ：test1

• Case sensitive sorting and results ：

 

                 

                

                

4. Manipulating databases

(1)  view the database

show databases;

                 

 (2) Show create statement

show create database  Database name ;

  explain :

• MySQL It is suggested that we use uppercase for keywords , But it's not necessary .
• Backquotes for database names ' ' , This is to prevent the database name used from being just a keyword
• /*!40100 default.... */ This is not a comment , At present mysql The version is greater than 4.01 edition , Just carry out this sentence

                         

(3) modify the database

ALTER DATABASE db_name [alter_spacification [,alter_spacification]...] 

alter_spacification: 
[DEFAULT] CHARACTER SET charset_name 
[DEFAULT] COLLATE collation_name

•   Modifying the database mainly refers to modifying the character set of the database , Validation rules

example ： take test1  The database character set is changed to gbk  

                                 

(4) Database deletion

DROP DATABASE [IF EXISTS] db_ name;

The result after deletion :

• The corresponding database cannot be seen inside the database
• The corresponding database folder is deleted , cascading deletion , All the data tables inside have been deleted
• Be careful ： Do not delete the database at will

                 

                

                

5. Backup and recovery  

(1) Backup

# mysqldump -P3306 -u root -p  password  -B  Database name  >  File path of database backup storage 

① Example ： take test2 Back up the library to a file （ Exit connection ）

                 

② see  test.sql The contents of the document , In fact, we create the entire database , Build table , The statements that import data are loaded with this document In the piece .

• The so-called backup , The essence is to put history on mysql All historical operations of the specified database , Make a backup .
• mysql How can I know that I have entered those in history sql Commands and data ?  mysql You should know ,binlog, Almost all operations on the specified database are recorded !

                 

(2) Restore

mysql> source  Backup data path 

                

(3) matters needing attention

① If you are not backing up the entire database , But one of the tables , How do you do it? ？

• # mysqldump -u root -p Database name Table name 1 Table name 2 > D:/mytest.sql

② Backing up multiple databases at the same time

• # mysqldump -u root -p -B Database name 1 Database name 2 ... > Database storage path

③ If you back up a database , No belt. -B Parameters , When restoring the database , You need to create an empty database first , Then use the database , Reuse source To restore .

 

                                        

                

6. Check the connection

• Can tell us which users are currently connected to our MySQL, If you find out that a user is not logged in normally , It is likely that your database is Someone invaded . Later, when you find that your database is slow , You can use this command to check the database connection

        

show processlist

• id            #ID identification , want kill A sentence is very useful
• use         # Currently connected users
• host        # Show which... This connection comes from ip On which port of
• db            # Database name
• command     # Connection status , Usually dormant （sleep）, Inquire about （query）, Connect （connect）
• time        # Connection duration , The unit is seconds
• state        # Show the current sql The state of the statement
• info          # Show this sql sentence