Mysql36 database backup and recovery

One . Physical backup and logical backup

The physical backup ： Backup data files , Dump database physical files to a directory . Physical backup recovery is faster , But it takes up a lot of space ,MySQL Can be used in the xtrabackup Tools for physical backup .
Logical backup ： Use tools to export database objects , Summary into backup file . Slow recovery of logical backup , But it takes up little space , More flexible .MySQL The common logical backup tool in is mysqldump . Logical backup is Backup sql sentence , Performing a backup at the time of recovery sql Statement to achieve the reproduction of database data .

Two . mysqldump Realize logical backup

2.1. Back up a database

Basic grammar ：

mysqldump –u  User name  –h  Host name  –p password   Name of the database to be backed up [tbname, [tbname...]]>  Backup filename 
 call .sql

explain ： The file name with suffix... Is not required .sql, For example, the suffix is .txt Your files are also OK .
give an example ： Use root User backup zyy_master_slave database ：

mysqldump -uroot -p zyy_master_slave>zyy_master_slave.sql
mysqldump -uroot -p zyy_master_slave > /var/lib/mysql/cptest/zyy_master_slave.sql

vim zyy_master_slave.sql

2.2. Back up all databases

If you want to use mysqldump Back up the entire instance , have access to --all-databases or -A Parameters ：

mysqldump -uroot -pxxxxxx --all-databases > all_database.sql
mysqldump -uroot -pxxxxxx -A > all_database.sql

2.3. Backup part of the database

Use --databases or -B Parameters , This parameter is followed by the database name , Multiple databases are separated by spaces . If specified databases Parameters , There will be a statement to create the database in the backup file , If no parameters are specified , There is no . The grammar is as follows ：

mysqldump –u user –h host –p --databases [ Database name 1 [ Database name 2...]] >  Backup file name .sql

give an example ：

mysqldump -uroot -p --databases zyy_master_slave dbtest3>two_database.sql
 perhaps 
mysqldump -uroot -p -B zyy_master_slave dbtest3 > two_database.sql

2.4. Back up some tables

such as , Make a backup before the table changes . The grammar is as follows ：

mysqldump –u user –h host –p  Database name  [ Table name 1 [ Table name 2...]] >  Backup file name .sql

give an example ： Backup zyy_master_slave Database based student surface

mysqldump -uroot -p zyy_master_slave student> student.sql

student.sql The contents of the document are as follows

You can see ,student The file is similar to the backed up library file . The difference is ,student The file contains only book surface DROP、CREATE and INSERT sentence .
To back up multiple tables, use the following command , Such as backup mytbl and student surface ：

# Back up multiple tables 
mysqldump -uroot -p zyy_master_slave mytbl student> 2_tables_bak.sql

2.5. Backup some data of single table

Sometimes a table has a lot of data , We just need some data . It can be used at this time --where Options. .where The conditions to be met are attached .
give an example ： Backup student In the table id Less than 10 The data of ：

mysqldump -uroot -p zyy_master_slave student --where="id < 10 " > student_part_id10_low_bak.sql

2.6. Exclude backups of some tables

If we want to back up a library , But some tables have a large amount of data or are not related to the business , At this time, we can consider excluding these watches , alike , Options --ignore-table You can do this .

mysqldump -uroot -p zyy_master_slave --ignore-table=zyy_master_slave .student > no_stu_bak.sql

By specifying as follows, it is determined that there is no... In the file student Table structure ：

grep "student" no_stu_bak.sql

2.7. Back up only the structure or only the data

Only the backup structure can be used --no-data Shorthand for -d Options ; Only backup data can be used --no-create-info Shorthand for -t Options

• Just back up the structure

mysqldump -uroot -p zyy_master_slave --no-data > no_data_bak.sql
# Use grep command , Can't find insert Related statements , Indicates that there is no data backup .
grep "INSERT" no_data_bak.sql

• Backup data only

mysqldump -uroot -p zyy_master_slave --no-create-info > atguigu_no_create_info_bak.sql
# Use grep command , Can't find create Related statements , Indicates that there is no data structure .
grep "CREATE" atguigu_no_create_info_bak.sql

2.8. The backup contains stored procedures 、 function 、 event

mysqldump Backup does not contain stored procedures by default , Custom functions and events . have access to --routines or -R Option to back up stored procedures and functions , Use --events or -E Parameters to back up events .
give an example ： Back up the entire MYSQLTEST library , Contains stored procedures and events ：

• Use the following SQL You can view which stored procedures or functions exist in the current library

SELECT SPECIFIC_NAME,ROUTINE_TYPE ,ROUTINE_SCHEMA FROM information_schema.Routines WHERE ROUTINE_SCHEMA="MYSQLTEST";

Now back up MYSQLTEST Database data , Functions and stored procedures .

mysqldump -uroot -p -R -E --databases MYSQLTEST> fun_MYSQLTEST_bak.sql

Query whether the function exists in the backup file , As shown below , You can see that it does contain functions .

2.9. mysqldump Common options

mysqldump Other common options are as follows ：

1. –add-drop-database： At every CREATE DATABASE Add before statement DROP DATABASE sentence .
2. –add-drop-tables： At every CREATE TABLE Add before statement DROP TABLE sentence .
3. –add-locking： use LOCK TABLES and UNLOCK TABLES Statement references each table dump . Insert faster when reloading dump files .
4. –all-database, -A： Dump all tables in all databases . And use –database The options are the same , Name all databases on the command line .
5. –comment[=0|1]： If set to 0, It is forbidden to dump other information in the file , For example, program version 、 Server version and host .–skip-comments And –comments=0 Same result for . The default value is 1, Include additional information .
6. –compact： Produce a small amount of output . This option disables annotations and enables –skip-add-drop-tables、–no-set-names、–skip-disable-keys and –skip-add-locking Options .
7. –compatible=name： Generated with other database systems or old MySQL Server more compatible output , The value can be ansi、MySQL323、MySQL40、postgresql、oracle、mssql、db2、maxdb、no_key_options、no_table_options perhaps no_field_options.
8. –complete_insert, -c： Use the complete INSERT sentence .
9. –debug[=debug_options], -#[debug_options]： Write debug log .
10. –delete,-D： Empty table before importing text file .
11. –default-character-set=charset： Use charsets Default character set . If not specified , Just use utf8.
12. –delete–master-logs： On the primary replication server , Delete the binary log after the dump operation . This option is automatically enabled -master-data.
13. –extended-insert,-e： Use includes several VALUES Multiple lines of the list INSERT grammar . This makes the dump file smaller , Reloading files can speed up insertion .
14. –flush-logs,-F： Refresh before starting dump MySQL Server log files . This option requires RELOAD jurisdiction .
15. –force,-f： During table dump , Even if SQL Mistakes continue .
16. –lock-all-tables,-x： Lock all tables in all databases . In the overall dump process, it is realized by global locking . This option turns off automatically
17. –single-transaction and –lock-tables.
18. –lock-tables,-l： Lock all tables before starting dump . use READ LOCAL Lock the table to allow parallel inserts MyISAM surface . For the transaction table （ for example InnoDB and BDB）,–single-transaction Is a better option , Because it doesn't need to lock the table at all .
19. –no-create-db,-n： This option disables CREATE DATABASE /!32312 IF NOT EXIST/db_name sentence , If given –database or –all-database Options , It is included in the output .
20. –no-create-info,-t： Export data only , Without adding CREATE TABLE sentence .
21. –no-data,-d： Do not write any row information of the table , Only dump the structure of the table .
22. –opt： This option is shorthand , It can dump quickly and produce a file that can be loaded quickly MySQL Dump file of the server . This option is on by default , But you can use –skip-opt Ban .
23. –password[=password],-p[password]： The password used when connecting to the server .-port=port_num,-P port_num： jointed TCP/IP Port number .
24. –protocol={TCP|SOCKET|PIPE|MEMORY}： Connection protocol used .
25. –replace,-r –replace and –ignore： Controls the processing of replacing or copying input records with existing records of unique key values . If specified –replace, The new row replaces the existing row with the same unique key value ; If specified –ignore, The input line that copies the existing unique key value is skipped . If you do not specify these two options , An error occurs when a duplicate key value is found , And ignore the rest of the text file .
26. –silent,-s： Silence mode . Output only when there is an error .
27. –socket=path,-S path： When the connection localhost Socket file used when （ For the default host ）.
28. –user=user_name,-u user_name： When connecting to the server MySQL User name used .
29. –verbose,-v： Lengthy mode , Print out the details of the program operation .
30. –xml,-X： produce XML Output .
    Run the help command mysqldump --help , You can get a complete list of options for a specific version .

 Tips   If you run mysqldump No, --quick or --opt Options ,mysqldump Load the whole result set before dumping the results 
 save . If you dump a large database, there may be problems , This option is enabled by default , But you can use --skip-opt Ban . If you use the most 
 The new version of the mysqldump Program backup data , And used to restore to the older version MySQL Server , Do not use --opt
 or -e Options .

3、 ... and . mysql Command restore data

Basic grammar ：

mysql –u root –p [dbname] < backup.sql

3.1. Restore a single database from a single database backup

Use root user , Back up the... From the previous exercise TRANTEST.sql The backup in the file is imported into the database , The order is as follows ：

• If the backup file contains a statement to create a database , The database name does not need to be specified during recovery , As shown below

mysql -uroot -p < TRANTEST.sq

• Otherwise, you need to specify the database name , As shown below

mysql -uroot -p TRANTEST< TRANTEST.sql

3.2. Full backup recovery

mysql –u root –p < all.sql
 perhaps 
mysql -uroot -pxxxxxx < all.sql

After the execution ,MySQL The database has been restored all.sql All files in the database .

3.3. Restore a single library from a full backup

There may be such a need , For example, we just want to restore a certain library , But we have backup of the whole instance , At this time, we can separate the backup of a single database from the full backup .
give an example ：

sed -n '/^-- Current Database: `TRANTEST`/,/^-- Current Database: `/p' all_database.sql
> TRANTEST.sql

# After the separation, we can import atguigu.sql You can restore a single library 

3.4. Restore a single table from a single database backup

This demand is still quite common . For example, we know which watch is misoperated , Then you can use the method of single table recovery to restore .
give an example ： We have TRANTEST Backup of the entire library , But because of student Table misoperation , You need to restore this form alone .

use TRANTEST;
# Delete student
DROP table student;
# View the tables in the Library 
show tables;

# First separate the statement of creating table 
cat TRANTEST.sql | sed -e '/./{H;$!d;}' -e 'x;/CREATE TABLE `student`/!d;q' > student.sql

# Then separate the insert table statement 
cat TRANTEST.sql | grep --ignore-case 'insert into `student`' > StudentData.sql

Then import

mysql -uroot -p TRANTEST<student.sql
mysql -uroot -p TRANTEST<StudentData.sql

Reexamine

use TRANTEST;
SHOW TABLES;

SELECT * FROM student;

Four . The physical backup ： Directly copy the entire database

Direct will MySQL Copy the database files in . This is the easiest way , And the fastest .MySQL The location of the database directory is not necessarily the same ：

• stay Windows Under the platform ,MySQL 8.0 The directory where the database is stored is usually... By default “ C:\ProgramData\MySQL\MySQL Server 8.0\Data ” Or other user-defined directories ;
• stay Linux Under the platform , The database directory location is usually /var/lib/mysql/;
• stay MAC OSX Under the platform , The database directory location is usually “/usr/local/mysql/data”;
  But in order to ensure the consistency of backup . Need assurance ：
• The way 1： Before backup , Stop the server .
• The way 2： Before backup , Execute... On related tables FLUSH TABLES WITH READ LOCK operation . In this way, when copying files in the database directory , Allow other customers to continue to query the table . meanwhile ,FLUSH TABLES Statement to ensure that all active index pages are written to the hard disk before starting the backup .
  This way is convenient 、 Fast , But not the best backup method , Because the actual situation may Stop... Is not allowed MySQL The server perhaps Lock the watch , And this method Yes InnoDB Storage engine The table of does not apply . about MyISAM The table that stores the engine , This makes backup and restore easy , But it's better to restore the same version MySQL database , Otherwise, there may be different file types .
  Be careful , After the physical backup , perform UNLOCK TABLES To settle the modification of the table by other customers .

 explain ：  stay MySQL In the version number , The first number indicates the major version number , With the same major version number MySQL The database file format is the same .

Besides , You can also consider using relevant tools to realize backup . such as , MySQLhotcopy Tools .MySQLhotcopy It's a Perl Script , It USES LOCK TABLES、FLUSH TABLES and cp or scp To quickly back up the database . It's the fastest way to back up a database or a single table , But it can only run on the machine where the database directory is located , And can only back up MyISAM Type of watch . be chiefly used in mysql5.5 Before .

5、 ... and . Physical recovery ： Copy directly to the database directory

step ：
1） Show me how to delete the data of the specified table in the backed up database .
2） Copy the backed up database data to the data directory , And restart MySQL The server .
3） Query whether the data of related tables are recovered . You need to use the following chown operation .
requirement ：

• It must be ensured that the database of the backup data and the database server to be restored have the same major version number . Because only MySQL When the main version number of the database is the same , To ensure these two MySQL The database file type is the same .
• This way is right MyISAM Table of type is more effective , about InnoDB Tables of type are not available . because InnoDB Table spaces cannot be copied directly .
• stay Linux Under the operating system , After copying to the database directory , Be sure to change the users and groups of the database into mysql, The order is as follows ：

chown -R mysql.mysql /var/lib/mysql/dbname

among , Two mysql Represent groups and users respectively ;“-R” Parameters can change the users and groups of all sub files in the folder ;“dbname” The parameter represents the database directory .

 Tips  Linux The permission setting under the operating system is very strict . Usually ,MySQL Database only root Users and mysql user 
 Under group mysql Users can access , Therefore, after copying the database directory to the specified folder , Be sure to use chown The order will 
 The user group of the folder becomes mysql, Change the user to mysql

6、 ... and . Export and import of tables

6.1. Export of tables

6.1.1. Use SELECT…INTO OUTFILE Export text file

stay MySQL in , have access to SELECT…INTO OUTFILE Statement to export the contents of the table into a text file .
give an example ： Use SELECT…INTO OUTFILE take TRANTEST In the database student Export the records in the table to a text file .
（1） Select database TRANTEST, And query student surface , The results are shown below .

USE TRANTEST;
SELECT * FROM student;

（2）mysql There are permission restrictions on the exported directory by default , That is, when using the command line for export , You need to specify a directory to operate .
Inquire about secure_file_priv value ：

show global variables like '%secure%';

（3） The results above show ,secure_file_priv The value of the variable is /var/lib/mysql-files/, Set the export directory to this directory ,SQL The statement is as follows .

SELECT * FROM student INTO OUTFILE "/var/lib/mysql-files/student.txt";

（4） see /var/lib/mysql-files/account.txt` file .

cd /var/lib/mysql-files/
vim student.txt 

6.1.2. Use mysqldump Command to export a text file

First, the previously generated student.txt Delete

# Delete student.txt
rm -rf student.txt
# View the files in this directory 
ll

give an example 1： Use mysqldump Command will TRANTEST In the database student Export the records in the table to a text file :

mysqldump -uroot -p -T "/var/lib/mysql-files" TRANTEST student

mysqldump After the command is executed , In the specified directory /var/lib/mysql-files/ Now I have student.sql and student.txt file .

open student.sql file , Its content includes creating student Tabular CREATE sentence .

open student.txt file , Its content only includes student Table data .

give an example 2： Use mysqldump take atguigu In the database account Export table to text file , Use FIELDS Options , Commas are required between fields “,” interval , All character type field values are enclosed in double quotes ：
First, the previously generated student.txt and student.sql Delete

# Delete student.txt
rm -rf student.txt
# Delete student.sql
rm -rf student.sql
# View the files in this directory 
ll

mysqldump -uroot -p -T "/var/lib/mysql-files/" TRANTEST student --fields-terminated-by=',' --fields-optionally-enclosed-by='\"'

sentence mysqldump After the statement is executed successfully , Two files will appear in the specified directory student .sql and student .txt.
open student .sql file , Its content includes creating student Tabular CREATE sentence .( Same as before )
open student .txt file , Its content includes creating account The data table . As can be seen from the document , Fields are separated by commas , The value of the character type is enclosed in double quotes .

6.1.3. Use mysql Command to export a text file

give an example 1： Use mysql Statement export TRANTEST In the data student Record in table to text file ：

mysql -uroot -p --execute="SELECT * FROM student;" TRANTEST > "/var/lib/mysql-files/student.txt"

give an example 2： take atguigu database account Export the records in the table to a text file , Use –veritcal Parameter displays the condition record in multiple lines ：

mysql -uroot -p --vertical --execute="SELECT * FROM student;" TRANTEST >"/var/lib/mysql-files/student.txt"

open student.txt file , Its content includes creating student The data table .

give an example 3： take TRANTEST database student The records in the table are exported to xml file , Use –xml Parameters , The specific sentences are as follows .

mysql -uroot -p --xml --execute="SELECT * FROM student;" TRANTEST >"/var/lib/mysql-files/student.xml"

explain ： If you want to export table data to html In file , have access to --html Options . Then you can use your browser to open .

6.2. Table import

6.2.1. Use LOAD DATA INFILE To import a text file

give an example 1：
Use SELECT…INTO OUTFILE take TRANTEST In the database student Export the records of the table to a text file

SELECT * FROM TRANTEST.student INTO OUTFILE '/var/lib/mysql-files/student.txt';

Delete student Table data ：

DELETE FROM TRANTEST.student;

From a text file account.txt Recovering data in ：

LOAD DATA INFILE '/var/lib/mysql-files/student.txt' INTO TABLE TRANTEST.student;

Inquire about student Table data ：

 select * from student;

give an example 2： Select database TRANTEST, Use SELECT…INTO OUTFILE take TRANTEST database student Export the records in the table to a text file , Use FIELDS Options and LINES Options , Commas are required between fields "," interval , All field values are enclosed in double quotes ：

SELECT * FROM TRANTEST.student INTO OUTFILE '/var/lib/mysql-files/student.txt' FIELDS
TERMINATED BY ',' ENCLOSED BY '\"';

Delete student Table data ：

DELETE FROM TRANTEST.student;

from /var/lib/mysql-files/student.txt Import data to student In the table ：

LOAD DATA INFILE '/var/lib/mysql-files/student.txt' INTO TABLE TRANTEST.student FIELDS TERMINATED BY ',' ENCLOSED BY '\"';

Inquire about student Table data , Specifically SQL as follows ：

select * from student;

6.2.2. Use mysqlimport To import a text file

give an example ：
export file student.txt, Use commas between fields "," interval , The field values are enclosed in double quotes ：

SELECT * FROM TRANTEST.student INTO OUTFILE '/var/lib/mysql-files/student.txt' FIELDS TERMINATED BY ',' ENCLOSED BY '\"';

Delete student Table data ：

DELETE FROM TRANTEST.student;

Use mysqlimport The order will student.txt Import the contents of the file into the database TRANTEST Of student In the table ：

mysqlimport -uroot -p TRANTEST '/var/lib/mysql-files/student.txt' --fields-terminated-by=',' --fields-optionally-enclosed-by='\"'

Inquire about account Table data ：

select * from student;

7、 ... and . Database migration

7.1. summary

Data migration （data migration） It's about choice 、 Get ready 、 Extract and transform data , The process of transferring data permanently from one computer storage system to another . Besides , Verify the integrity of the migrated data and Decommission the old data storage , It's also considered part of the whole data migration process .
The reasons for database migration are diverse , Including server or storage device replacement 、 Maintain or upgrade , Application migration , Website integration , Disaster recovery and data center migration .
Different migration schemes may be adopted according to different requirements , But on the whole ,MySQL Data migration schemes can be roughly divided into Physical migration and Logical migration Two types of . Usually as far as possible automation By , So as to liberate human resources from tedious tasks .

7.2. Migration plan

• Physical migration
  Physical migration is suitable for the overall migration of large amount of data . The advantage of using the physical migration scheme is that it is relatively fast , But it needs to be down for migration and it requires MySQL The version and configuration must be the same as the original server , It can also cause unknown problems .
  Physical migration includes copying data files and using XtraBackup There are two backup tools .
  Physical migration can be used between the same server , We can install the same version of database software on the new server , Create the same directory , It is suggested that the configuration file should be the same as the original database , Then copy the data file and log file from the original database , Configure file group permissions , Then use it on the new server side mysqld Command start database .
• Logical migration
  Logical transfer is more applicable , Whether it's Partial migration still Full migration , You can use logical migration . The most commonly used method in logical migration is through mysqldump And other backup tools .

7.3. Pay attention to migration

7.3.1. Precautions for migrating between databases of the same version

It refers to those with the same major version number MySQL Move databases between databases .
The way 1： Because before and after migration MySQL Database The main version number is the same , Therefore, database migration can be realized by copying the database directory , But physical migration is only applicable to MyISAM The engine's table . about InnoDB surface , The database cannot be backed up by directly copying files .
The way 2： The most common and safest way is to use mysqldump command Derived data , Then use... In the target database server MySQL Command import .
give an example ：

#host1 Back up all databases in your machine , And migrate the database to a database named host2 On the machine 
mysqldump –h host1 –uroot –p –-all-databases|
mysql –h host2 –uroot –p

In the above statement ,“|” The symbol represents the pipe , Its function is to mysqldump Backup files to mysql command ;“–all-databases” Indicates that you want to migrate all databases . In this way, the migration can be realized directly .

7.3.2. Precautions for migration between different versions of databases

for example , It turns out that many servers use 5.7 Version of MySQL database , stay 8.0 After the version is pushed out , Improved 5.7 Many defects of the version , Therefore, the database needs to be upgraded to 8.0 edition .
Between the old version and the new version MySQL Different default character sets may be used , For example, some old versions use latin1 As default character set , And the latest version of MySQL The default character set is utf8mb4. If there is Chinese data in the database , In the process of migration, we need to Modify the default character set , Otherwise, the data may not be displayed normally .
The high version of the MySQL Databases usually Compatible with lower versions , Therefore, it can be from the lower version of MySQL Migrate the database to a higher version MySQL database .

7.3.3. Precautions for migration between different databases

Migration between different databases refers to the migration from other types of databases to MySQL database , Or from MySQL Database migration to other types of databases . There is no universal solution to this migration .
Before moving , You need to understand the architecture of different databases , Compare the differences between them . Defining the same type of data in different databases Keywords may be different . for example ,MySQL The date field in is divided into DATE and TIME Two kinds of , and ORACLE The date field is only DATE;SQL Server It's in the database ntext、Image And so on ,MySQL The database does not have these data types ;MySQL Supported by ENUM and SET type , these SQL Server Database does not support .
in addition , The database vendor did not fully comply with SQL Standard to design database system , Lead to different database systems SQL sentence There are differences . for example , Microsoft SQL Server The software uses T-SQL sentence ,T-SQL It contains non-standard SQL sentence , Unable to join MySQL Of SQL Statement compatibility .
The differences between different types of databases cause mutual The difficulty of migration , These differences are actually technical barriers deliberately created by commercial companies . But the migration between different types of databases is not It's not totally impossible . for example , have access to MyODBC Realization MySQL and SQL Server Migration between .MySQL Official tools MySQL Migration Toolkit You can also migrate data between different data .MySQL Migrate to Oracle when , Need to use mysqldump Command export sql file , then , Manually change sql In the document CREATE sentence .

7.4. Migration summary

8、 ... and . Delete database processing

8.1. delete： Delete lines by mistake

1. It's safer to recover data , yes Restore a backup , Or find a slave library as Temporary storage , Perform these operations on this temporary Library , Then we will confirm the data of the temporary database , Restore to the main library . If you modify the main library directly , This may result in a of data Secondary destruction .
2. Of course , Aiming at the problem of preventing erroneous deletion of data , Recommendations are as follows ：

-  hold  sql_safe_updates  Parameter set to  on . thus , If we forget to be in delete perhaps update Write in statement where Conditions , perhaps where If there is no index field in the condition , The execution of this statement will report an error .
-  If you are sure to delete all the data in a small table , In setting up the sql_safe_updates=on Under the circumstances , Can be in delete Add to statement where Conditions , such as where id>=0.
-  Before the code goes online , Must go through  SQL Audit  .

8.2. truncate/drop ： Erasure Library / surface

programme ：
In this case , To recover data , You need to use Full volume backup , Add Incremental log The way of the . This solution requires regular full backup online , And back up in real time binlog.
In the case of both conditions , If someone is at noon 12 I deleted a library by mistake , The process of data recovery is as follows ：

1. Take the most recent Full volume backup , Let's say that this library is available once a day , The last backup was the same day In the morning 2 spot ;
2. Restore a with a backup Temporary storage ;
3. From the log backup , Take it out in the morning 2 Post order log ;
4. Put these logs , Except for the statement of deleting data by mistake , All applied to temporary storage .

8.3. Delay copying the standby database

If there is Very central The business of , Too long recovery time is not allowed , Consider setting up a standby database for delayed replication . The problem with the general primary and secondary replication structure is , If a table in the main database is deleted by mistake , This command will soon be sent to all slaves , In turn, all the data tables from the database are deleted by mistake .
A delayed replication standby is a special kind of standby , adopt CHANGE MASTER TO MASTER_DELAY = N command , You can specify that the standby database keep the same as the primary database N Second delay . For example, you put N Set to 3600, This means that if there is data deleted by mistake on the main database , And in 1 This misoperation order was found within hours , This command has not been executed in the standby database for delayed replication . At this time, execute on this standby database stop slave, And then through the methods introduced before , Skip misoperation command , You can recover the data you need .

8.4. Prevent deleting database by mistake / The method of table

1. Account separation . The purpose of this is , Avoid writing wrong orders . such as ：

-  Only for business development students DML jurisdiction , But not to truncate/drop jurisdiction . And if business developers have DDL If you need it , It can be supported by developing a management system .
-  Even if it's DBA Team members , It is also stipulated that only   Read only account  , Only use the account with update permission when necessary .

2. Set up operation specifications . such as ：

-  Before deleting the data table , Must first   Change the name of the watch   operation . then , Observe for a while , Make sure there is no impact on the business before deleting this table .
-  When changing the name of the watch , A fixed suffix is required for the table name （ For example, add  _to_be_deleted ), Then the action of deleting the table must be performed through the management system . also , When the management system deletes a table , Only tables with fixed suffixes can be deleted .

8.5. rm： False deletion MySQL example

For a MySQL For clusters , Never mind rm Delete data 了 . Just delete the data of one of the nodes ,HA The system will start working , Choose a new main library , So as to ensure the normal operation of the whole cluster . All we have to do is recover the data on this node , Then connect to the whole cluster .

Nine . appendix ：MySQL Common commands

9.1. mysql

The mysql Don't mean mysql service , But to mysql Client tools .
grammar ：

mysql [options] [database]

9.1.1. Connection options

# Parameters  ：
-u, --user=name  Specify user name 
-p, --password[=name]  Specified password 
-h, --host=name  Specify the server IP Or domain name 
-P, --port=#  Specify the connection port 
# Example  ：
mysql -h 127.0.0.1 -P 3306 -u root -p
mysql -h127.0.0.1 -P3306 -uroot -p password 

9.1.2. Execution Options

-e, --execute=name  perform SQL Statement and exit 

This option is available in Mysql Client execution SQL sentence , Instead of connecting to MySQL The database then executes , For some batch scripts , This is especially convenient .

# Example ：
mysql -uroot -p TRANTEST -e "select * from student";

9.2. mysqladmin

mysqladmin Is a client program that performs administrative operations . It can be used to check the configuration and current state of the server 、 Create and delete databases, etc .
Can pass ： mysqladmin --help Command to view help documents

# Example  ：
mysqladmin -uroot -p create 'test01';
mysqladmin -uroot -p drop 'test01';
mysqladmin -uroot -p version;

9.3. mysqlbinlog

Because the binary log file generated by the server is saved in binary format , So if you want to check the text format of these texts , Will be used to mysqlbinlog Log management tools .
grammar ：

mysqlbinlog [options] log-files1 log-files2 ...

# Options ：
-d, --database=name :  Specify database name , Only the specified database related operations are listed .
-o, --offset=# :  Ignore the previous in the log n Line command .
-r,--result-file=name :  Output the output text format log to the specified file .
-s, --short-form :  Show simple format ,  Omit some information .
--start-datatime=date1 --stop-datetime=date2 :  All logs within the specified date interval .
--start-position=pos1 --stop-position=pos2 :  All logs within the specified location interval .

9.4. mysqldump

mysqldump Client tools are used to back up databases or migrate data between different databases . The backup includes creating tables , And insert the SQL sentence .
grammar ：

mysqldump [options] db_name [tables]
mysqldump [options] --database/-B db1 [db2 db3...]
mysqldump [options] --all-databases/-A

9.4.1. Connection options

# Parameters  ：
-u, --user=name  Specify user name 
-p, --password[=name]  Specified password 
-h, --host=name  Specify the server IP Or domain name 
-P, --port=#  Specify the connection port 

9.4.2. Output content options

# Parameters ：
--add-drop-database  Add... Before each database creation statement  Drop database  sentence 
--add-drop-table  Add... Before each table creation statement  Drop table  sentence  ,  Default on  ;  Don't open  (--
skip-add-drop-table)
-n, --no-create-db  Do not include database creation statements 
-t, --no-create-info  Create statement without data table 
-d --no-data  No data 
-T, --tab=name  Automatically generate two files ： One .sql file , Statement to create a table structure ;
 One .txt file , Data files , amount to select into outfile

# Example  ：
mysqldump -uroot -p db01 tb_book --add-drop-database --add-drop-table > a
mysqldump -uroot -p -T /tmp test city

9.5. mysqlimport/source

mysqlimport Is the client data import tool , Used to import mysqldump Add -T The text file exported after the parameter .
grammar ：

mysqlimport [options] db_name textfile1 [textfile2...]

Example ：

mysqlimport -uroot -p test /tmp/city.txt

If you need to import sql file , have access to mysql Medium source Instructions :

source /root/tb_book.sql

9.6. mysqlshow

mysqlshow Client object finder , Used to quickly find which databases exist 、 Tables in the database 、 A column or index in a table .
grammar ：

mysqlshow [options] [db_name [table_name [col_name]]]

Parameters ：

--count  Display statistics of databases and tables （ database , surface   You can not specify ）
-i  Display the status information of the specified database or table 

Example ：

# Query the number of tables in each database and the number of records in the table 
mysqlshow -uroot -p --count

# Inquire about test The fields in each table in the library , And the number of lines 
mysqlshow -uroot -p TRANTEST --count

# Inquire about TRANTEST In the library student Details of the table 
mysqlshow -uroot -p TRANTEST student --count