MySQL配置文件、MySQL数据库存储引擎

目录

• 一、字符编码与配置文件
  • 1.\s查看mysql相关信息
  • 2.默认配置文件
  • 3.mac配置mysql
  • 4.利用配置文件免登录
• 二、数据库存储引擎
  • 1.查看常见存储引擎的方式
  • 2.需要了解的四个存储引擎
    • （1）MyISAM
    • （2）InnoDB
    • （3）MEMORY
    • （4）BLACKHOLE
    • （5）使用四种引擎创建数据表产生文件类型不同

一、字符编码与配置文件

1.\s查看mysql相关信息

当前用户、版本、编码、端口号

2.默认配置文件

默认配置文件是my-default.ini

拷贝之后并重命名为my-ini

1.utf8mb4可以存储emoji表情

2.utf8和utf-8是不同的

修改了配置文件之后需要重启服务端

3.mac配置mysql

1）访达查找快捷键 command+shift+G

2）手动创建my.cof

sudo vim /etc/my.cnf

3）按 i 进入编辑状态，将下方内容粘贴进去，按esc退出编辑状态，按shift+zz保存并退出

# Example MySQL config file for medium systems.  
  #  
  # This is for a system with little memory (32M - 64M) where MySQL plays  
  # an important part, or systems up to 128M where MySQL is used together with  
  # other programs (such as a web server)  
  #  
  # MySQL programs look for option files in a set of  
  # locations which depend on the deployment platform.  
  # You can copy this option file to one of those  
  # locations. For information about these locations, see:  
  # http://dev.mysql.com/doc/mysql/en/option-files.html  
  #  
  # In this file, you can use all long options that a program supports.  
  # If you want to know which options a program supports, run the program  
  # with the "--help" option.  
  # The following options will be passed to all MySQL clients  
  [client]
  default-character-set=utf8
  #password   = your_password  
  port        = 3306  
  socket      = /tmp/mysql.sock   
  # Here follows entries for some specific programs  
  # The MySQL server  
  [mysqld]
  character-set-server=utf8
  init_connect='SET NAMES utf8
  port        = 3306  
  socket      = /tmp/mysql.sock  
  skip-external-locking  
  key_buffer_size = 16M  
  max_allowed_packet = 1M  
  table_open_cache = 64  
  sort_buffer_size = 512K  
  net_buffer_length = 8K  
  read_buffer_size = 256K  
  read_rnd_buffer_size = 512K  
  myisam_sort_buffer_size = 8M  
  character-set-server=utf8  
  init_connect='SET NAMES utf8' 
# Don't listen on a TCP/IP port at all. This can be a security enhancement,  
# if all processes that need to connect to mysqld run on the same host.  
# All interaction with mysqld must be made via Unix sockets or named pipes.  
# Note that using this option without enabling named pipes on Windows  
# (via the "enable-named-pipe" option) will render mysqld useless!  
#   
#skip-networking  
  
  # Replication Master Server (default)  
  # binary logging is required for replication  
  log-bin=mysql-bin  
    
    # binary logging format - mixed recommended  
    binlog_format=mixed  
      
      # required unique id between 1 and 2^32 - 1  
      # defaults to 1 if master-host is not set  
      # but will not function as a master if omitted  
      server-id   = 1  
        
    # Replication Slave (comment out master section to use this)  
    #  
    # To configure this host as a replication slave, you can choose between  
    # two methods :  
    #  
    # 1) Use the CHANGE MASTER TO command (fully described in our manual) -  
    #    the syntax is:  
    #  
    #    CHANGE MASTER TO MASTER_HOST=<host>, MASTER_PORT=<port>,  
    #    MASTER_USER=<user>, MASTER_PASSWORD=<password> ;  
    #  
    #    where you replace <host>, <user>, <password> by quoted strings and  
    #    <port> by the master's port number (3306 by default).  
    #  
    #    Example:  
    #  
    #    CHANGE MASTER TO MASTER_HOST='125.564.12.1', MASTER_PORT=3306,  
    #    MASTER_USER='joe', MASTER_PASSWORD='secret';  
    #  
    # OR  
    #  
    # 2) Set the variables below. However, in case you choose this method, then  
    #    start replication for the first time (even unsuccessfully, for example  
    #    if you mistyped the password in master-password and the slave fails to  
    #    connect), the slave will create a master.info file, and any later  
    #    change in this file to the variables' values below will be ignored and  
    #    overridden by the content of the master.info file, unless you shutdown  
    #    the slave server, delete master.info and restart the slaver server.  
    #    For that reason, you may want to leave the lines below untouched  
    #    (commented) and instead use CHANGE MASTER TO (see above)  
    #  
    # required unique id between 2 and 2^32 - 1  
    # (and different from the master)  
    # defaults to 2 if master-host is set  
    # but will not function as a slave if omitted  
    #server-id       = 2  
    #  
    # The replication master for this slave - required  
    #master-host     =   <hostname>  
    #  
    # The username the slave will use for authentication when connecting  
    # to the master - required  
    #master-user     =   <username>  
    #  
    # The password the slave will authenticate with when connecting to  
    # the master - required  
    #master-password =   <password>  
    #  
    # The port the master is listening on.  
    # optional - defaults to 3306  
    #master-port     =  <port>  
    #  
    # binary logging - not required for slaves, but recommended  
    #log-bin=mysql-bin  
      
      # Uncomment the following if you are using InnoDB tables  
      #innodb_data_home_dir = /usr/local/mysql/data  
      #innodb_data_file_path = ibdata1:10M:autoextend  
      #innodb_log_group_home_dir = /usr/local/mysql/data  
      # You can set .._buffer_pool_size up to 50 - 80 %  
      # of RAM but beware of setting memory usage too high  
      #innodb_buffer_pool_size = 16M  
      #innodb_additional_mem_pool_size = 2M  
      # Set .._log_file_size to 25 % of buffer pool size  
      #innodb_log_file_size = 5M  
      #innodb_log_buffer_size = 8M  
      #innodb_flush_log_at_trx_commit = 1  
      #innodb_lock_wait_timeout = 50  
        
        [mysqldump]  
        quick  
        max_allowed_packet = 16M  
          
          [mysql]  
          no-auto-rehash  
          # Remove the next comment character if you are not familiar with SQL  
          #safe-updates  
          default-character-set=utf8   
            
        [myisamchk]  
        key_buffer_size = 20M  
        sort_buffer_size = 20M  
        read_buffer = 2M  
        write_buffer = 2M  
          
          [mysqlhotcopy]  
          interactive-timeout
 
		[mysqld]
		skip-grant-tables

4）重启mysql服务

4.利用配置文件免登录

我们还可以不用输入账号和密码登录

将管理员的账号和密码直接吸在配置文件中，只要在终端中输入mysql即可登录

[mysql]  # 在mysql的客户端中添加账号和密码
 user='root'
 password=123

二、数据库存储引擎

存储引擎： 数据库针对数据采取的多种存取方式

1.查看常见存储引擎的方式

输入 show engines即可查询存储引擎

mysql> show engines;

2.需要了解的四个存储引擎

（1）MyISAM

存储数据的速度快，但是不支持行锁等功能，安全性较低

MyISAM storage engine    
   
mysql版本 5.5及之前默认的存储引擎

（2）InnoDB

支持事务、行锁、外键等操作，存储数据的速度没有MyISAM快，但是安全性较高

Supports transactions, row-level locking, and foreign keys 
 
mysql版本 5.5之后的默认的存储引擎

（3）MEMORY

基于内存存储数据，仅用户临时表数据存取

当mysql服务端关闭并重启，也就是mysql在内存中清空并丢失后，使用memory引擎的数据表中的数据就会丢失

Hash based, stored in memory, useful for temporary tables 

（4）BLACKHOLE

写入数据后会立刻丢失

/dev/null storage engine (anything you write to it disappears)

事务 transactions：

往通俗的讲就是，事务就是一个整体，里面的内容要么都执行成功，要么都不成功。不可能存在部分执行成功而部分执行不成功的情况。

就是说如果单元中某条sql语句一旦执行失败或者产生错误，那么整个单元将会回滚(返回最初状态)。所有受到影响的数据将返回到事务开始之前的状态，但是如果单元中的所有sql语句都执行成功的话，那么该事务也就被顺利执行。

行锁 row-level locking：对一行行的数据进行加锁，同一时间点只能有一个人去操作这个数据

外键 foreign keys：建立表的关系

（5）使用四种引擎创建数据表产生文件类型不同

create database db2;
use db2;
create table t1(id int) engine=myisam;
create table t2(id int) engine=innodb;
create table t3(id int) engine=memory;
create table t4(id int) engine=blackhole;

在终端中使用

mysql> create database db2;
Query OK, 1 row affected (0.02 sec)
 
mysql> use db2;
Database changed
mysql> create table t1(id int) engine=myisam;
Query OK, 0 rows affected (0.05 sec)
 
mysql> create table t2(id int) engine=innodb;
Query OK, 0 rows affected (0.05 sec)
 
mysql> create table t3(id int) engine=memory;
Query OK, 0 rows affected (0.04 sec)
 
mysql> create table t4(id int) engine=blackhole;
Query OK, 0 rows affected (0.05 sec)
 

创建成功后可以在db2文件夹中看到数据表的文件

存储引擎	表结构文件	表数据文件	表索引文件
myisam	.frm	.MYD	.MYI
innodb	.frm	.ibd	-
MEMORY	.frm	-	-
BLACKHOLE	.frm	-	-

• 引擎为myisam的数据表有3个文件

myisam单独将索引列出来了，因此myisam引擎的存取速度较快

• 引擎为innodb的数据表有2个文件

innodb将表数据和索引放在同个文件中，因此其索引效率较myisam慢

• 引擎为MEMORY的数据表有1个文件

MEMORY引擎将数据存储在内存中

当mysql关闭并重启，随即mysql的数据在内存中清空后，使用memory引擎的数据表中的数据就会丢失

• 引擎为BLACKHOLE的数据表有1个文件