Database theory

The concept of the database

Use file to manage data

1. Management is not convenient 

2. File operational efficiency

3. The data generated by a program can not be shared

There arises a database

　　Nature: the part of the saved data is saved to a public place all the relevant data related to the user must be the place to find public

If supplementary computer database of stored fat fried so his data would all gone so there will be more computer database to store data sharing 

The MySQL database

　　Is essentially a web-based application to communicate
　　any underlying network-based communications software are socket

Analog mysql server

　　- socket-based communication

　　- messaging

　　- SQL statement (actually a common standard)

Analog mysql client

　　- socket-based communication

　　- messaging

　　- SQL statement (actually a common standard)

ps: MySQL not only supports MySQL client to operate also support other programming languages ​​directly manipulate python java c ++ php syntax is not the same

DBMS data management system

　　Into a relational database (there may be between the data associated with limitations)

　　　　　 Relational databases are usually table structure, which means you are using a relational database when the first step is to determine the structure of the table

　　　　　 To find out what is the record: record is in the file (in the table) of rows of data

　　　　　 Added: Library: a list of folders: one file    field: written in the first row of the table data    fields: Field Name Field Type +

　　　　　　　　Field specific type of memory used in the name string 

　　　　　　　　　　　　　　　 Digital access password used

　　　　　　　　　　　　　　　 The date of deposit with birthday

　　　　　　　　Common non-relational database MySQL (free open source performance is not bad support a large number of high concurrency)

　　　　　　　　　　　　　　　　　　   SQLserver (Microsoft's products only support windows)

　　　　　　　　　　　　　　　　　　  Oracle (Database of most cattle B, but high fees)

　　　　　　　　　　　　　　　　　　   DB2 (surcharge)

　　　　  Non-relational databases

　　　　　　　　Usually in the form of k, v storing key data (speed cache)

　　　　　　　　redis, mongodb (document database is very close to non-relational data relational), memcache

MySQL can actually see it as a software support remote file operations

Installing MySQL 
    in the IT industry do not easily try the latest version of the software 

after downloading is the MySQL server and client download down 
    decompression 
    view the file directory 

    server 
        mysqld 
    client 
        mysql 

    to start mysqld 
        1 . Switch to the bin directory under
         2 Executive mysqld 

    PS: do pre-configured MySQL when the terminal is recommended that you run as administrator 

    Windows + r to start an ordinary user 

    mysql landing at the time of the initial password is not directly enter 

    the end mysql sql statement is a semicolon do not knock you completely did not enter a semicolon default 
    client will let you continue typing

mysql installation

mysql sql statement is a semicolon does not knock you completely do not enter a semicolon default
client will let you continue typing

SQL statements

    The client landed 
        MySQL -h 127.0 . 0.1 -P 3306 -uroot-- the p- 
        can be abbreviated 
        MySQL -uroot-- the p- 

        If you do not enter a user name and password by default is landed guest mode function can be used in very few 

    clients logout 
        Exit; 
        quit; 
    View all databases 
        show databases; 


    view a process 
        tasklist | (! to exit this to view) findstr name 

    to kill the process 
        taskkill / F / PID process ID 




production environment variable 
    to start the path to the file where the environment variable added to the system's 
    attention : Once you've configured a while to restart the mysql server and terminal cmd 

will mysqld made into a system service (the computer starts, the client automatically start, as long as the client can start)
    Production system services your administrator cmd terminal must be a 

    mysqld -install (To quit all cmd, and then re-open, enter the command directly!) 



to change the password 
    without a password 
        mysqladmin -uroot--p password 123 
    under have a password 
        mysqladmin -uroot--p123 password 123456 

    when the command input the wrong time can \ c cancel the previous command cancel 

crack the code 
    will now have to start the server stopped 

    1 . skip authentication user name and password to start the server 
        mysqld --skip-grant- the tables start the server to skip the authorization table
     2 . modify the administrator password corresponding to the user 
        Update the mysql.user SET password = password ( 123 ) WHERE user = ' the root ' and Host = ' localhost ' ;
     . 3 . Close this manner the server to re-authenticate the username and password to start
     4 normal manner username and password mysql server connection 

profile 
    \ s simple configuration view mysql server 
    configuration file normally suffix We are ini the end of the 

    mysql configuration file that comes not to modify 
    , but you can create a configuration file my.ini 
    mysql server will automatically load the configuration in your configuration file in the startup my.ini 

    need to first modify the configuration file after completing service end stop restart to take effect 

    modified the configuration file must restart the server 


basic operation of the database 
    library similar to folders 
        by 
            create database db1; 
        check 
            show databases; check all 
            show create database db1; check the individual 
        to change 
            the ALTER database db1 charset = ' GBK '; Modifying coding  
        delete
            drop database db1; delete database 
    tables 
        need to specify the library when you create a table of 
            the specified library: use library name 
            to view the current, although in the library: the SELECT Database () 

        by 
            the Create the Table UserInfo (the above mentioned id int , name char ); 

        check 
            show tables; a library view all the tables below 
            Show Create table UserInfo; 
            desc UserInfo;     <==> DESCRIBE UserInfo; 
        modified 
            ALTER Modify table UserInfo name char ( 32 ); 
        puncturing 
            drop table userinfo; 


    record
        Create to a library or specify an existing library
        Switch to this library to create the table 
        and then the operation record 
        Create Database DB1; 
        Create Table UserInfo (ID int , name char ( 32 ), password int ); 

        by 
            INSERT UserInfo values (INTO . 1 , ' Jason ' , 123 ); inserting a single data 
            INTO UserInfo values INSERT ( . 1 , ' Jason ' , 123 ), ( 2 , ' Egon ' , 123 ), ( . 3 , ' Tank ', 123 ); a plurality of data inserted 
        check 
            SELECT * from UserInfo; field information of all query
             SELECT name from UserInfo; field information query specifies
             SELECT ID, name from UserInfo WHERE ID = . 1 or name = Tank; information field with filter conditions 
        change 
            Update UserInfo SET name = ' Kevin '  WHERE ID = . 1 ; a modified data field information 
            Update UserInfo SET name = ' Jason ' , password =666  WHERE ID = . 1 ; a plurality of data fields modify 
        delete 
            Delete from UserInfo WHERE ID = . 1 ; designated qualified data deletion 
            Delete from UserInfo; delete all the data in the table