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MySQL的知识点有什么

发布时间：2021-12-21 12:35:08 所属栏目：MySql教程 来源：互联网
导读：本篇内容主要讲解MySQL的知识点有哪些，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习MySQL的知识点有哪些吧! 1.在CentOS6 上 MySQL重新部署 1.1 先删除 日志文件和数据文件 rm -rf arch/* data/* 1.2 再进行安
本篇内容主要讲解“MySQL的知识点有哪些”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“MySQL的知识点有哪些”吧!
 
1.在CentOS6 上 MySQL重新部署
    1.1  先删除 日志文件和数据文件   
        rm -rf arch/*  data/*      
    1.2   再进行安装    
        scripts/mysql_install_db  --user=mysqladmin --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data
2. 空密码修改
    show databases;   -- 查看数据库列表
        mysql> show databases;
        +--------------------+
        | Database           |
        +--------------------+
        | information_schema |
        | mysql              |
        | performance_schema |
        | test               |
        | testdb             |
        +--------------------+
        5 rows in set (0.00 sec)
 
    use mysql;           -- 使用mysql数据库
        mysql> use mysql;
        Database changed
 
    show tables;        -- 查看mysql数据库里面的table列表
        mysql> show tables;
        +---------------------------+
        | Tables_in_mysql           |
        +---------------------------+
        | columns_priv              |
        | db                        |
        | event                     |
        | func                      |
        | general_log               |
        | help_category             |
        | help_keyword              |
        | help_relation             |
        | help_topic                |
        | innodb_index_stats        |
        | innodb_table_stats        |
        | ndb_binlog_index          |
        | plugin                    |
        | proc                      |
        | procs_priv                |
        | proxies_priv              |
        | servers                   |
        | slave_master_info         |
        | slave_relay_log_info      |
        | slave_worker_info         |
        | slow_log                  |
        | tables_priv               |
        | time_zone                 |
        | time_zone_leap_second     |
        | time_zone_name            |
        | time_zone_transition      |
        | time_zone_transition_type |
        | user                      |
        +---------------------------+
        28 rows in set (0.00 sec)
 
    desc user;           -- 查看user表的表结构
    mysql> desc user;
     +------------------------+-----------------------------------+------+-----+-----------------------+-------+
     | Field                  | Type                              | Null | Key | Default               | Extra |
     +------------------------+-----------------------------------+------+-----+-----------------------+-------+
      | Host                   | char(60)                          | NO   | PRI |                       |       |
      | User                   | char(16)                          | NO   | PRI |                       |       |
      | Password               | char(41)                          | NO   |     |                       |       |
      | Select_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Insert_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Update_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Delete_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Drop_priv              | enum('N','Y')                     | NO   |     | N                     |       |
      | Reload_priv            | enum('N','Y')                     | NO   |     | N                     |       |
      | Shutdown_priv          | enum('N','Y')                     | NO   |     | N                     |       |
      | Process_priv           | enum('N','Y')                     | NO   |     | N                     |       |
      | File_priv              | enum('N','Y')                     | NO   |     | N                     |       |
      | Grant_priv             | enum('N','Y')                     | NO   |     | N                     |       |
      | References_priv        | enum('N','Y')                     | NO   |     | N                     |       |
      | Index_priv             | enum('N','Y')                     | NO   |     | N                     |       |
      | Alter_priv             | enum('N','Y')                     | NO   |     | N                     |       |
      | Show_db_priv           | enum('N','Y')                     | NO   |     | N                     |       |
      | Super_priv             | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_tmp_table_priv  | enum('N','Y')                     | NO   |     | N                     |       |
      | Lock_tables_priv       | enum('N','Y')                     | NO   |     | N                     |       |
      | Execute_priv           | enum('N','Y')                     | NO   |     | N                     |       |
      | Repl_slave_priv        | enum('N','Y')                     | NO   |     | N                     |       |
      | Repl_client_priv       | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_view_priv       | enum('N','Y')                     | NO   |     | N                     |       |
      | Show_view_priv         | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_routine_priv    | enum('N','Y')                     | NO   |     | N                     |       |
      | Alter_routine_priv     | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_user_priv       | enum('N','Y')                     | NO   |     | N                     |       |
      | Event_priv             | enum('N','Y')                     | NO   |     | N                     |       |
      | Trigger_priv           | enum('N','Y')                     | NO   |     | N                     |       |
      | Create_tablespace_priv | enum('N','Y')                     | NO   |     | N                     |       |
      | ssl_type               | enum('','ANY','X509','SPECIFIED') | NO   |     |                       |       |
      | ssl_cipher             | blob                              | NO   |     | NULL                  |       |
      | x509_issuer            | blob                              | NO   |     | NULL                  |       |
      | x509_subject           | blob                              | NO   |     | NULL                  |       |
      | max_questions          | int(11) unsigned                  | NO   |     | 0                     |       |
      | max_updates            | int(11) unsigned                  | NO   |     | 0                     |       |
      | max_connections        | int(11) unsigned                  | NO   |     | 0                     |       |
      | max_user_connections   | int(11) unsigned                  | NO   |     | 0                     |       |
      | plugin                 | char(64)                          | YES  |     | mysql_native_password |       |
      | authentication_string  | text                              | YES  |     | NULL                  |       |
      | password_expired       | enum('N','Y')                     | NO   |     | N                     |       |
      +------------------------+-
 
    show create table user;   -- 查看user表的表结构，包含user表的创建脚本
        mysql> show create table user G;
        *************************** 1. row ***************************
               Table: user
        Create Table: CREATE TABLE `user` (
          `Host` char(60) COLLATE utf8_bin NOT NULL DEFAULT '',
          `User` char(16) COLLATE utf8_bin NOT NULL DEFAULT '',
          `Password` char(41) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT '',
          `Select_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Insert_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Update_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Delete_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Drop_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Reload_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Shutdown_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Process_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `File_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Grant_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `References_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Index_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Alter_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Show_db_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Super_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_tmp_table_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Lock_tables_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Execute_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Repl_slave_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Repl_client_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Show_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Alter_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_user_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Event_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Trigger_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `Create_tablespace_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          `ssl_type` enum('','ANY','X509','SPECIFIED') CHARACTER SET utf8 NOT NULL DEFAULT '',
          `ssl_cipher` blob NOT NULL,
          `x509_issuer` blob NOT NULL,
          `x509_subject` blob NOT NULL,
          `max_questions` int(11) unsigned NOT NULL DEFAULT '0',
          `max_updates` int(11) unsigned NOT NULL DEFAULT '0',
          `max_connections` int(11) unsigned NOT NULL DEFAULT '0',
          `max_user_connections` int(11) unsigned NOT NULL DEFAULT '0',
          `plugin` char(64) COLLATE utf8_bin DEFAULT 'mysql_native_password',
          `authentication_string` text COLLATE utf8_bin,
          `password_expired` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
          PRIMARY KEY (`Host`,`User`)
        ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global privileges'
        1 row in set (0.00 sec)
 
 
    -- 查询 user表的允许访问的地址，登录名和登录密码
    mysql> select Host,user,password from mysql.user;
    +-----------+------+----------+
    | Host      | user | password |
    +-----------+------+----------+
    | localhost | root |          |
    | hadoop000 | root |          |
    | 127.0.0.1 | root |          |
    | ::1       | root |          |
    | localhost |      |          |
    | hadoop000 |      |          |
    +-----------+------+----------+
    6 rows in set (0.00 sec)
 
    -- 修改root账号的密码
    mysql> update mysql.user set password=password('123456') where user='root';
    Query OK, 4 rows affected (0.03 sec)
    Rows matched: 4  Changed: 4  Warnings: 0
 
    -- 查询修改后的信息
    mysql> select Host,user,password from mysql.user;
    +-----------+------+-------------------------------------------+
    | Host      | user | password                                  |
    +-----------+------+-------------------------------------------+
    | localhost | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
    | hadoop000 | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
    | 127.0.0.1 | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
    | ::1       | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
    | localhost |      |                                           |
    | hadoop000 |      |                                           |
    +-----------+------+-------------------------------------------+
    6 rows in set (0.00 sec)
 
    --  使修改生效
    mysql> flush privileges;
    mysql用户的权限操作，最后加 flush privileges;
 
3. 修改% 任意机器可访问
    --  将 hadoop000 修改为'%'后，表示任意机器都可访问
    mysql> update mysql.user set Host='%' where Host='hadoop000';
    Query OK, 1 row affected (0.00 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    -- 使修改生效
    mysql>  flush privileges;
    Query OK, 0 rows affected (0.00 sec)
 
4. mysql命令参数
    mysql -uroot -p123456         -- 可以正常登录
    mysql -u root -p123456        -- 可以正常登录
    mysql -u root -p 123456      -- 不可以正常登录 -p后面有空格
    mysql -u root -p123456 -h292.168.137.251  -- 可以正常登录 带IP登录
    mysql -u root -p123456 -hlocalhost mysql   -- 可以正登录 指定登录的数据库
 
5. 创建新DB和用户
    -- 创建数据库
    mysql> create database testdb;
    Query OK, 1 row affected (0.09 sec)
    -- 授权登录数据库的用户名和密码
    mysql> grant all privileges on testdb to root@'%' identified by '123456';
    Query OK, 0 rows affected (0.16 sec)
    -- 生效命令
    mysql> flush privileges;
    Query OK, 0 rows affected (0.05 sec)
 
6. 查看当前mysql链接数 （在工作中，可以适当kill连接，注意：慎用！！！）
    mysql> show processlist;
    +----+------+----------------------+-------+---------+------+-------+------------------+
    | Id | User | Host                 | db    | Command | Time | State | Info             |
    +----+------+----------------------+-------+---------+------+-------+------------------+
    |  7 | root | localhost            | mysql | Query   |    0 | init  | show processlist |
    | 11 | root | 192.168.90.157:63149 | NULL  | Sleep   |   13 |       | NULL             |
    +----+------+----------------------+-------+---------+------+-------+------------------+
    2 rows in set (0.00 sec)
 
 
    --  如果哪个process的卡，夯住，锁死，可以相关技术人员或相关责任人沟通好后kill掉
    kill Id;
 
7. MySQL字符类型 char 和 varchar 的对比
     相同点： char 和 varchar都是存储字符串的数据类型
    差异点：
                1 存数据时的区别
                  char定义的是固定长度，长度范围为0-255，存储时，如果字符数没有达到定义的位数，会在后面用空格补全存入数据库中。
                  varchar是变长长度，长度范围为0-65535，存储时，如果字符没有达到定义的位数，也不会在后面补空格。
               2 占用字节差别
                 以latin编码为便，一个字符占用一个字节。
    MySQL的知识点有哪些
可以用上表来表示，当定义char时，不管你存入多少字符，都会占用到你定义的字符数，而用varchar时，则和你输入的字符数有关，会多一到两个字节来记录字节长度，当数据位占用的字节数小于255时，用1个字节来记录长度，数据位占用字节数大于255时，用2个字节来记录长度，还有一位来记录是否为nul值。
 
8. MySQL 库名，表名和表数据的大小写问题
  8.1 库名和表名 默认是区分大小写的，列名不区分大小写：
        -- 列出数据库列表
        mysql> show databases;
        +--------------------+
        | Database           |
        +--------------------+
        | information_schema |
        | mysql              |
        | performance_schema |
        | test               |
        | testdb             |
        +--------------------+
        5 rows in set (0.00 sec)
        -- 更改数据库，数据库名大小写，和数据库里面的数据库名大小写不一致
        mysql> use TestDB;
        ERROR 1049 (42000): Unknown database 'TestDB'
        -- -- 更改数据库，数据库小写，和数据库里面的数据库名大小写一致
        mysql> use testdb;
        Database changed
        mysql> show tables;
        +------------------+
        | Tables_in_testdb |
        +------------------+
        | user             |
        +------------------+
        1 row in set (0.00 sec)
        -- 查询大写的表名，和数据库里面的表名大小写不一致
        mysql> select * from USER;
        ERROR 1146 (42S02): Table 'testdb.USER' doesn't exist
        -- 查询小写的表名，和数据库里面的表名大小写一致
        mysql> select * from user;
        +------+----------+
        | id   | name     |
        +------+----------+
        |    1 | ZHANGSAN |
        |    2 | zhangsan |
        +------+----------+
        2 rows in set (0.00 sec)
        -- 查询user表结构
        mysql> desc user;
        +-------+--------------+------+-----+---------+-------+
        | Field | Type         | Null | Key | Default | Extra |
        +-------+--------------+------+-----+---------+-------+
        | id    | int(11)      | YES  |     | NULL    |       |
        | name  | varchar(200) | YES  |     | NULL    |       |
        +-------+--------------+------+-----+---------+-------+
        2 rows in set (0.02 sec)
        -- 查询user表数据，列名大写，不影响查询，说明表列名不区分大小写。        mysql> select ID,NAME from user;
        +------+----------+
        | ID   | NAME     |
        +------+----------+
        |    1 | ZHANGSAN |
        |    2 | zhangsan |
        +------+----------+
        2 rows in set (0.00 sec)
 
     解决库名和表名 区分大小写的方法：在 /etc/my.cnf   文件里面添加 lower_case_table_names=1 配置。
 
 
   8.2  表数据默认是不区分大小写的。可以通过binary关键字加以解决区分大小写。
          8.2.1.  在查询的sql语句后面加上 binary关键字。
            -- 不加关键字查询
             mysql> select * from user where name='zhangsan';
              +------+----------+
               | id   | name     |
              +------+----------+
               |    1 | ZHANGSAN |
               |    2 | zhangsan |
              +------+----------+
            2 rows in set (0.00 sec)
            -- 加关键字查询
            mysql> select * from user where binary  name='zhangsan';
            +------+----------+
            | id   | name     |
            +------+----------+
            |    2 | zhangsan |
            +------+----------+
            1 row in set (0.03 sec)
 
        8.2.2.  在建表时上 binary关键字
 
             -- 将user表删除后再重建
 
            mysql> drop table user;
            Query OK, 0 rows affected (0.04 sec)
            mysql>  CREATE TABLE `user` (
                ->   `id` int(11) DEFAULT NULL,
                ->   `name` varchar(200) binary  DEFAULT NULL
                -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8
                -> ;
            Query OK, 0 rows affected (0.04 sec)
 
            -- 查询 user表的数据
 
            mysql> select * from user;
            +------+----------+
            | id   | name     |
            +------+----------+
            |    1 | ZHANGSAN |
            |    2 | zhangsan |
            +------+----------+
            2 rows in set (0.00 sec)
            -- 不带 binary关键字的条件查询
            mysql> select * from user where name='zhangsan';
            +------+----------+
            | id   | name     |
            +------+----------+
            |    2 | zhangsan |
            +------+----------+
            1 row in set (0.02 sec)
 
    9. 修改mysql客户端及服务器的字符集
        9.1 修改数据库客户端字符集
            修改/etc/my.cnf配置文件如下：
            [client]
            port            = 3306
            socket          = /usr/local/mysql/data/mysql.sock
            default-character-set=utf8
 
        9.2 查看参数文件
            mysql> show variables like 'character%';
            +--------------------------+----------------------------+
            | Variable_name            | Value                      |
            +--------------------------+----------------------------+
            | character_set_client     | utf8                       |
            | character_set_connection | utf8                       |
            | character_set_database   | latin1                     |
            | character_set_filesystem | binary                     |
            | character_set_results    | utf8                       |
            | character_set_server     | latin1                     |
            | character_set_system     | utf8                       |
            | character_sets_dir       | /usr/local/mysql/share/charsets/ |
            +--------------------------+----------------------------+
            8 rows in set (0.01 sec)
 
        9.3 修改服务器参数文件
            [mysqld]
            port=3306
            character-set-server=utf8           -- 设置MySQL服务器编码
            init-connect='SET NAMES utf8'   -- 设置connectioin 的编码
            socket          = /usr/local/mysql/data/mysql.sock
 
到此，相信大家对“MySQL的知识点有哪些”有了更深的了解，不妨来实际操作一番吧！这里是亿速云网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！

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