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
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
