Mysql---- import and export & View & Index & execution plan

Catalog

Preface

One 、 Import and export

Two 、 View

​ edit   3、 ... and 、 Indexes

Four 、 Implementation plan

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Preface

Last time I shared MySQL Function of , The content of this sharing is , Import and export 、 View 、 Index and execution plan

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One 、 Import and export

1. Using tools , similar Sqlyog、Navicat Wait to import and export data .

        1.1 export （Navicat）

 

  Select the file save path

        1.2 Import

Select the table , Select run SQL file

Choose SQL file  

2. Use mysqldump Import and export

  2.1 export

    2.1.1 Export table data and table structure

  
    mysqldump -u user name -p password Database name > Database name .sql( This name is casually called ) 

    #/usr/local/mysql/bin mysqldump -uroot -pabc >abc.sql
    After typing enter, you will be prompted to output the password

   
    notes ： The exported data is in mysql Of bin Under the table of contents

  2.2 Import

    Be careful ： First, create an empty database

    mysql>create database abc;

    2.2.1 Method 1

    mysql>use abc;                   # Select database
    mysql>set names utf8;            # Set database encoding
    mysql>source /home/abc/abc.sql;  # Import data

    2.2.2 Method 2

    mysql -u user name -p password Database name < Database name .sql
    #mysql -uabc_f -p abc < abc.sql

3.LOAD DATA INFILE

  You can go through first SELECT INTO OUTFILE The way , Export data to Mysql Of C:\ProgramData\MySQL\MySQL Server 5.5\data Under the table of contents , Re pass LOAD DATA INFILE Mode import . 

  1) select * from Table name into outfile '/ file name .sql';
  2) load data infile '/ file name .sql' into table Table name ( Name 1,...); 

  Be careful ： Authorization is required, otherwise it cannot be exported successfully

In our MySQL Under the installation directory of my.ini Authorization in document

 

Two 、 View

 1. What is a view

   1) A view is a virtual table , A table derived from one or more tables in a database .    
   2) The definition of view is stored in the database , There is no data stored in view , The data is stored in the original table .
   3) When using views to query data , The database system will take the corresponding data from the original table .    
   
  2. The function of view

   1) Make the operation simple .
   2) Increase data security .
   3) Improve the logical independence of tables .

   3. Basic grammar
   
   CREATE VIEW View name AS SELECT sentence ;

Be careful ： On the premise of successful view creation, duplicate columns cannot appear

  3、 ... and 、 Indexes

 1. What is index

    An index is a combination of one or more columns in a database table , Its function is to improve the query speed of data in the table .
A catalogue similar to a book , Easy and fast positioning , Find the specified content .

   2. Advantages and disadvantages of index

    advantage ： Speed up data query .
    shortcoming ： The time to create and maintain indexes has increased , At the same time, it takes up hard disk space .

   3. Index classification

   1) General index ： Is the most basic index , It has no restrictions ;

Be careful ： The corresponding column values of unique key indexes are not allowed to be the same  

   2) unique index ： Similar to the previous normal index , The difference is that ： The value of the index column must be unique , But you can have an empty value . If it's a composite index , The combination of column values must be unique ;

   3) primary key ： Is a special unique index , A table can only have one primary key , No null values are allowed ;

 

   4) Composite index ： An index created on multiple fields , Only the first field that created the index is used in the query criteria , Indexes are used . When using a composite index, follow the leftmost prefix set ;

Follow the leftmost segment matching principle

 

 

   5) Full-text index ： Use FULLTEXT Parameters can be set , Full text index can only be created in CHAR,VARCHAR,TEXT Type field on . The main function is to improve the speed of querying larger string types ; Only MyISAM The engine supports the index ,MySQL The default engine does not support ;mysql5.7+

    Word segmentation is   The Chinese / the people / republic

   4. Create index

   CREATE [UNIQUE|FULLTEXT] INDEX Index name ON Table name ( Field name [( length )][ASC|DESC])

   5. Modify the index

   ALTER TABLE Table name ADD [UNIQUE|FULLTEXT] INDEX Index name ( Field name [( length )][ASC|DESC])

   6. Delete index

   DROP INDEX Index name ON Table name

Four 、 Implementation plan

  We import case data

 

explain select * from t_user u left join t_role r on u.roleid = r.roleid

 

explain select * from t_user u where u.roleid = (select roleid from t_role where rolename = ' Administrators ')

 

 

explain select * from t_user u left join t_role r on u.roleid = r.roleid

 

explain select * from t_user u right join t_role r on u.roleid = r.roleid

 

 id The higher the priority, the higher

1、 like Key left cannot be added %

2、or The conditional column segment of a link cannot be a column segment without an index

3、 The data type of query criteria must be a value

4、 Avoid using ！=

5、 Sorting will invalidate the index

6、 The leftmost paragraph implements the principle