MySQL transactions, indexes, data recovery and backup

MySQL transaction processing

• Transaction is to put a group of SQL statements in the same batch to execute
• If an SQL statement fails, all SQL in the batch will be cancelled

Transaction characteristics

• Atomicity
• Consistency
• Isolation
• Durability

MySQL transaction realization method
SET AUTOCOMMIT

• Use the SET statement to change the automatic submission mode
• SET AUTOCOMMIT = 0; # 关闭自动提交模式 SET AUTOCOMMIT = 1; # 开启自动提交模式
• The default is automatic submission in MySQL
• Turn off auto-commit first when using transactions

note

开启事务
SHOW VARIABLES LIKE 'event_scheduler';
设置数据库支持事务
SET GLOBAL  event_scheduler=ON;

MySQL transaction implementation method
START TRANSACTION
Start a transaction, mark the starting point of the transaction
COMMIT
Submit a transaction to the database
ROLLBACK
Roll back the transaction and return the data to the initial state of the transaction
SET AUTOCOMMIT = 1;
Enable automatic submission of MySQL database

MySQL transaction processing steps

Database index

effect

1. Improve query speed to ensure the uniqueness of data
2. Can accelerate the connection between the table and the table to achieve the referential integrity between the table and the table
3. When using grouping and sorting clauses for data retrieval, the time for grouping and sorting can be significantly reduced
4. Full-text search field for search optimization

classification

• Primary key index (PRIMARY KEY)
• Unique index (UNIQUE)
• Regular Index (INDEX)
• Full text index (FULLTEXT

Primary key index
A certain attribute or combination of attributes can uniquely identify a record
Such as: student table (student number, name, class, gender, etc.), the student number is uniquely identified and can be used as the primary key
Features

• The most common index types
• Ensure the uniqueness of data records
• Determine the location of specific data records in the database

Unique index (UNIQUE)
effect
Avoid duplication of values ​​in a data column in the same table
The difference with the primary key index
There can be only one primary key index
and multiple unique indexes

Regular Index (INDEX)
effect: Quickly locate specific data
note
Both index and key keywords can be set for regular indexes, which
should be added to the search condition field. It is
not advisable to add too many regular indexes, which will affect data insertion, deletion and modification operations

Full text index (FULLTEXT)
effect: Quickly locate specific data
note
Can only be used for data tables of MyISAM type
Can only be used for CHAR, VARCHAR, TEXT data column types
Suitable for large data sets

Manage index
Create index

• Add when creating table
• Append after table creation

ALERT TABLE 表名 ADD  索引类型（数据列名）

Delete index

DROP  INDEX 索引名 ON    表名
ALTER TABLE 表名   DROP  INDEX  索引名
ALTER TABLE 表名   DROP  PRIMARY KEY

View index

SHOW  INDEX(或KEYS) FROM 表名

Index guidelines

• Indexes are not as many as possible
• Don't index frequently changing data
• It is recommended not to add indexes for tables with small data volumes
• The index should generally be added to the search condition field

MySQL backup

Database backup necessity
Ensure that important data is not lost
Data transfer

MySQL database backup method
mysqldump backup tool
Database management tools, such as SQLyog
directly copy database files and related configuration files

mysqldump database backup
effect
Dump database,
collect database for backup,
transfer data to another SQL server (not necessarily MySQL service)

mysqldump  -h 主机名 –u 用户名 –p   [options]   数据库名  
[ table1 table2 table3 ]   > path/filename.sql

 # 备份myschool数据库如： 
 > mysqldump -u root -p  myschool > d:/myschool.sql
  EnterPassword: *****

mysqldump common options


MySQL database recovery
method one
Use SOURCE syntax

SOURCE     /path/db_name.sql;

/path/ is an absolute path, and must be a file that the mysql running user has permission to read
SOURCE Execute in the MySQL command line

Method two
use mysql client

mysql –u root –p  dbname  <  /path/db_name.sql;

Export and import data using SQL statements

Export

SELECT   *   INTO   OUTFILE   'file_name'  
    FROM   tbl_name

Import

LOAD   DATA   INFILE   'file_name '   
    INTO   TABLE   tbl_name[FIELDS]