MySQL常用命令基础操作

MySQL启动与更改密码

mysql启动基本原理说明：

/etc/init.d/mysqld是一个shell启动脚本，启动后最终会调用，mysqld_safe脚本，最后调用mysqld服务启动mysql，我们编辑/etc/init.d/mysqld，可以看到脚本，启动俩个进程mysqld和mysqld_safe，一般故障的时候我们用mysqld_safe来启动，

关闭mysql

1 mysqladmin - uroot -p密码 shut down
2 /etc/init.d/mysqld  stop
3 kill USR2`cat path/pid`

优雅的关闭mysql但是不建议用killall杀掉所有的mysql进程，这样会导致mysql数据库起不来，所以网友遇到这样情况也很多，

我们登陆mysql后想分清出那个是正式环境那个是测试环境，

命令行修改登陆提示符

mysql> prompt\u@king\s->
PROMPT set to '\u@king\s->'

配置文件修改登陆提示符

在my.cnf配置文件中[mysql]模块下添加如下内容，保存后，无需重启myysql，退出当前的session，重新登陆

[mysql]
prompt=\\u@king\s->

登陆mysql

[root @king~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is
Server version: 5.5. MySQL Community Server (GPL)
Copyright (c) , , Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>

更改root密码

 mysql> update user set password=password('') where user='root' and host='localhost';  #password（'12345'）是指定一个函数
 Query OK,  row affected (0.00 sec)
 Rows matched:   Changed:   Warnings:
 mysql> flush privileges;　　　　　　　　　　　　　　#刷新，没刷新前是在内存里面
 Query OK,  rows affected (0.17 sec)
 mysql>

说明，修改密码都需要刷新一下哦，linux找回mysql root用户密码

单实例mysql修改丢失root方法

1，首先停止mysql

/etc/init.d/mysql stop

2，使用--skip-grant-tables启动mysql，忽略授权登陆验证

 1 mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
 2 mysql -u root -p　　　　　　　　#说明-p登陆时密码是空，也可以不加-p，亲测哦(#^.^#)
 3 update mysql.user set password=password("newpassword") where user='root'and host='localhost';
 4 mysql> flush privileges;
 5 mysql> quit
 6 # /etc/init.d/mysql restart
 7 # mysql -uroot -p
 8 enter password: <输入新设的密码newpassword>
 9 mysql>

多实例mysql修改丢失root方法

1关闭mysql

killall mysqld

2启动时加--skip-grant-tables参数

mysql_safe --defaults-file=/data//my.cnf --skip-grant-tables& mysql -u root -p -S /data//mysql.sock

3修改密码

mysql>update mysql.user set password=password("newpassword") where user='root'and host='localhost';
mysql> flush privileges;
Query OK, 0 rows affected (0.03 sec)

SQl的分类

SQl结构化查询语言包含6个部分

1. 数据查询语言（DQL（data query language）），作用从表中获取数据，关键字select，
2. 数据操作语言（DMl（data manipulation language））作用处理表中的数据insert ，update，delete
3. 事务处理语言（TPL）关键字begin，commit和 rollback
4. 数据控制语言（DCl）grant（授权） 和revoke
5. 数据定义语言（DDl）create和drop在数据库中创建新表或删除表 alter
6. 指针控制语言（CCl） declare cursor， fetch into 和update where current用于对一个或多个表单独行的操作

查看数据库

show databases;或show database link '';或select database;

 1 mysql> show databases;
 2 +--------------------+
 3 | Database           |
 4 +--------------------+
 5 | information_schema |
 6 | mysql              |
 7 | performance_schema |
 8 | student            |
 9 | test               |
10 +--------------------+
11 8 rows in set (0.01 sec)

创建数据库

命令语法：create database <数据库名> 注意库名字不能数字开头

 mysql> create database king;
 Query OK,  row affected (0.01 sec)

 mysql> show databases;
 +--------------------+
 | Database           |
 +--------------------+
 | information_schema |
 | king               |
 | mysql              |
 | performance_schema |
 | student            |
 | test               |
 +--------------------+
 6 rows in set (0.01 sec)

 mysql> show create  database king\G
 *************************** . row ***************************
        Database: king
 Create Database: CREATE DATABASE `king` /*!40100 DEFAULT CHARACTER SET utf8 */
  row in set (0.00 sec)

 mysql>

创建一个指定字符集的数据库

 mysql> CREATE DATABASE db_name DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci; #红色指定编码，蓝色校验规则。
 Query OK,  row affected (0.01 sec)

删除数据库

drop  database <数据库名字>

 mysql> drop database test;
 Query OK,  row affected (0.07 sec)

 mysql> show databases;
 +--------------------+
 | Database           |
 +--------------------+
 | information_schema |
 | king               |
 | mysql              |
 | performance_schema |
 | student            |
 +--------------------+
 5 rows in set (0.01 sec)

连接数据库

命令：use <数据库名>相当于linux下的cd切换目录的命令，use是切换数据库

 mysql> use king;
 Database changed
 mysql> select database();   #查看当前的数据库，带（）相当于函数，
 +------------+
 | database() |
 +------------+
 | king       |
 +------------+
  row in set (0.00 sec)

查看数据库

select database （）;相当于linux下的pwd

 mysql> select version();　　　　#查看当前的版本
 +-----------+
 | version() |
 +-----------+
 | 5.5.    |
 +-----------+
  row in set (0.06 sec)
 mysql> select user();　　　　　　#查看当前的用户
 +----------------+
 | user()         |
 +----------------+
 | root@localhost |
 +----------------+
  row in set (0.04 sec)
 mysql> select now();　　　　　　#查看当前的时间
 +---------------------+
 | now()               |
 +---------------------+
 | -- :: |
 +---------------------+
  row in set (0.02 sec)
 mysql>

表操作

创建表并查看

create table <表名>（<字段名1><类型1>）;

 mysql> create table im(id int() not null, name varchar() not null default'QQ'　　　　#创建表id为int类型，name为varchar
 );
 Query OK,  rows affected (0.59 sec)
 mysql> show tables from king;　　　　　　　　　　　　　　#从king数据库中查看表
 +----------------+
 | Tables_in_king |
 +----------------+
 | im |
 +----------------+
  row in set (0.04 sec)
 mysql> desc im;　　　　　　　　　　　　　　　　　　　　#查看表结构
 +-------+-------------+------+-----+---------+-------+
 | Field | Type | Null | Key | Default | Extra |
 +-------+-------------+------+-----+---------+-------+
 | id | int() | NO | | NULL | |
 | name | varchar() | NO | | QQ | |
 +-------+-------------+------+-----+---------+-------+
  rows in set (0.22 sec)
 mysql>

show colums from im;查看表结构

 mysql> show create table im \G;　　　　　　　　#\G Send command to mysql server，display result vertically向MySQL服务器发送命令，垂直显示结果
 *************************** . row ***************************
        Table: im
 Create Table: CREATE TABLE `im` (
   `id` int() NOT NULL,
   `name` varchar() NOT NULL DEFAULT 'QQ'
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8
  row in set (0.64 sec)

mysql表的字段类型

列类型	需要的存储量
tinyint	1字节
smallint	2个字节
mediumint	3个字节
int	4个字节
integer	4个字节
bigint	8个字节
float（X）	4如果x<=24或8如果25<=X=53
float	4个字节
double	8个字节
double precision	8个字节
real	8个字节
decimal（M，D）	M字节（D+2，如果m<D）
numeric（M，D）	M字节（D+2，如果m<D）

为表的字段创建索引

创建主键索引，查询数据库，按主键查询是最快的，每一个表只有一个主键列，但是可以有多个普通的索引列，主键列要求列的内容必须唯一，而索引列不要求内容必须唯一。

create table student(
id int (4) not null auto_increment,
name char(20) not null,
age tinyint(2) not null default'0',
dept varchar(16) default null,
primary key (id),
key index_name(name));

 mysql> create table student( id int () not null auto_increment, name char() n
 ot null, age tinyint() not null default'',dept varchar() default null,primar
 y key (id), key index_name(name));
 Query OK,  rows affected (0.18 sec)

auto_increment自增，primary key (id), 主键，key index_name(name));普通索引，

 mysql> desc student;　　　　　　　　#查看创建的student表
 +-------+-------------+------+-----+---------+----------------+
 | Field | Type        | Null | Key | Default | Extra          |
 +-------+-------------+------+-----+---------+----------------+
 | id    | int()      | NO   | PRI | NULL    | auto_increment |
 | name  | char()    | NO   | MUL | NULL    |                |
 | age   | tinyint()  | NO   |     |        |                |
 | dept  | varchar() | YES  |     | NULL    |                |
 +-------+-------------+------+-----+---------+----------------+
  rows in set (0.17 sec)

alter table student drop  primary key ;　　　　　　删除主键，测试不行，

 mysql> alter table student drop  primary key ;
 ERROR  (): Incorrect table definition; there can be only one auto column and it must be defined as a key

　　　　　　　　　　　　　　　不正确的表定义；只能有一个自动COLUM它必须被定义为一个密钥

alter table student change id id int primary key auto_increment; 如果创建表忘记添加主键了，就执行这个。

创建普通索引分为唯一索引和普通索引

alter table student drop index index_name; # index固定索引，index_name是你创建表的时候的索引

alter table student add index index_name（name）;

create index index_name on student （name（8））; # index固定索引（固定写法），index_name 随便写但要见名知意， on student 在哪个表上（student）8就是前8个字符创建索引。

create index index_name_dept on student （name，dept）

按条件列查询数据时，联合索引是有前缀生效特性的 index（a，b，c）仅a，ab，abc三个查询条件列可以走索引

查看表的索引

 mysql> show index from student\G;
 *************************** . row ***************************
         Table: student
    Non_unique:
      Key_name: PRIMARY
  Seq_in_index:
   Column_name: id
     Collation: A
   Cardinality:
      Sub_part: NULL
        Packed: NULL
          Null:
    Index_type: BTREE
       Comment:
 Index_comment:
 *************************** . row ***************************
         Table: student
    Non_unique:
      Key_name: index_name
  Seq_in_index:
   Column_name: name
     Collation: A
   Cardinality:
      Sub_part: NULL
        Packed: NULL
          Null:
    Index_type: BTREE
       Comment:
 Index_comment:
  rows in set (0.00 sec)

创建唯一索引

create unique index uni on student（name）;

 mysql> create unique index uni on student (name);
 Query OK,  rows affected (0.09 sec)
 Records:   Duplicates:   Warnings:
 mysql> desc student;
 +-------+-------------+------+-----+---------+----------------+
 | Field | Type        | Null | Key | Default | Extra          |
 +-------+-------------+------+-----+---------+----------------+
 | id    | int()      | NO   | PRI | NULL    | auto_increment |
 | name  | char()    | NO   | UNI | NULL    |                |
 | age   | tinyint()  | NO   |     |        |                |
 | dept  | varchar() | YES  |     | NULL    |                |
 +-------+-------------+------+-----+---------+----------------+
  rows in set (0.02 sec)

1. 要在表的列上创建索引
2. 索引会加快查询的速度，但是会影响更新的速度
3. 索引不是越多越好，要在频繁查询的where后的条件列上创建索引
4. 小表或唯一值极少的列上不建索引，要在带包以及不同内容多的列上创建索引

往表中插入数据

create table test(

id int(4) not null auto_increment,

name char(20) not null,

primary key (id)

);

 mysql> create table test(id int() not null auto_increment, name char() not n
 ll,primary key (id));
 Query OK,  rows affected (0.01 sec)
 mysql> show tables;
 +----------------+
 | Tables_in_king |
 +----------------+
 | student        |
 | test           |
 +----------------+
  rows in set (0.00 sec)
 mysql> insert into test (id,name) values(,'boy');  #插入数据，主键自增我们直接插name，insert into test（name） values（'new'）;
 Query OK,  row affected (0.05 sec)
 mysql> select *from test;
 +----+------+
 | id | name |
 +----+------+
 |   | boy  |
 +----+------+
  row in set (0.04 sec)

mysql> delete from test;
Query OK,  row affected (0.05 sec)
mysql> select *from test;
Empty set (0.00 sec)
mysql> insert into test (id,name) values(,'boy'),(,'new');
Query OK,  rows affected (0.00 sec)
Records:   Duplicates:   Warnings: 

查询数据

select *from  表名;

 mysql> select *from test;
 +----+------+
 | id | name |
 +----+------+
 |   | boy  |
 |   | new  |
 +----+------+
  rows in set (0.47 sec)

指定条件查询

 mysql> select *from test where id =;　　　　#根据id查询
 +----+------+
 | id | name |
 +----+------+
 |   | boy  |
 +----+------+
  row in set (0.09 sec)

 mysql> select *from test where name='new';　　　　#根据name查询，字符串需要带引号
 +----+------+
 | id | name |
 +----+------+
 |   | new  |
 +----+------+
  row in set (0.03 sec)

多个条件查询and区交集，or取并集。排序 order by id desc（正序），sec（倒序）

 mysql> select *from test where name='new'or id=;
 +----+------+
 | id | name |
 +----+------+
 |   | boy  |
 |   | new  |
 +----+------+
  rows in set (0.08 sec)

explain查看索引、

 mysql> explain select *from test where name='new'\G;
 *************************** . row ***************************
            id:
   select_type: SIMPLE
         table: test
          type: ALL
 possible_keys: NULL
           key: NULL
       key_len: NULL　　　　#可以看到索引为空
           ref: NULL
          rows:
         Extra: Using where
  row in set (0.04 sec)

help explain;

修改表中指定条件固定列的数据

命令语法：update 表名 set 字段=新值，where 条件

 mysql> update test set name='wangxinxia' where id=;
 Query OK,  row affected (0.90 sec)
 Rows matched:   Changed:   Warnings:
 mysql> desc test;
 +-------+----------+------+-----+---------+----------------+
 | Field | Type     | Null | Key | Default | Extra          |
 +-------+----------+------+-----+---------+----------------+
 | id    | int()   | NO   | PRI | NULL    | auto_increment |
 | name  | char() | NO   |     | NULL    |                |
 +-------+----------+------+-----+---------+----------------+
  rows in set (0.25 sec)
 mysql> select* from test;
 +----+------------+
 | id | name       |
 +----+------------+
 |   | boy        |
 |   | wangxinxia |
 +----+------------+
  rows in set (0.00 sec)

truncate  table test;和delete from test的区别

1. truncate 更快，清空物理文件
2. delete逻辑清楚，按行删

删除数据

 mysql> delete from student where id=3;
 Query OK, 1 row affected (0.30 sec)
 mysql> show tables;
 +----------------+
 | Tables_in_king |
 +----------------+
 | student        |
 | test           |
 +----------------+
 2 rows in set (0.07 sec)
 mysql> select * from student;
 +----+----------+-----+-------+
 | id | name     | age | dept  |
 +----+----------+-----+-------+
 |  1 | zhangsan |  20 | yanfa |
 |  2 | zhaoliu  |  21 | dba   |
 +----+----------+-----+-------+

增删改表的字段

语法alter table 表名 add sex char（4）；

 mysql> alter table student add sex char (4);
 Query OK, 2 rows affected (0.54 sec)
 Records: 2  Duplicates: 0  Warnings: 0
 mysql> desc student;
 +-------+-------------+------+-----+---------+----------------+
 | Field | Type        | Null | Key | Default | Extra          |
 +-------+-------------+------+-----+---------+----------------+
 | id    | int(4)      | NO   | PRI | NULL    | auto_increment |
 | name  | char(20)    | NO   | UNI | NULL    |                |
 | age   | tinyint(2)  | NO   |     | 0       |                |
 | dept  | varchar(16) | YES  |     | NULL    |                |
 | sex   | char(4)     | YES  |     | NULL    |                |
 +-------+-------------+------+-----+---------+----------------+
 5 rows in set (0.20 sec)

alter table 表名 add qq varchar（10）first；

 mysql> alter table student add  qq varchar(10) first;
 Query OK, 2 rows affected (0.06 sec)
 Records: 2  Duplicates: 0  Warnings: 0
 mysql> desc student;
 +-------+-------------+------+-----+---------+----------------+
 | Field | Type        | Null | Key | Default | Extra          |
 +-------+-------------+------+-----+---------+----------------+
 | qq    | varchar(10) | YES  |     | NULL    |                |
 | id    | int(4)      | NO   | PRI | NULL    | auto_increment |
 | name  | char(20)    | NO   | UNI | NULL    |                |
 | age   | tinyint(2)  | NO   |     | 0       |                |
 | dept  | varchar(16) | YES  |     | NULL    |                |
 | sex   | char(4)     | YES  |     | NULL    |                |
 +-------+-------------+------+-----+---------+----------------+
 6 rows in set (0.02 sec)

rename table 原表to新表

 mysql> show tables;
 +----------------+
 | Tables_in_king |
 +----------------+
 | student        |
 | test           |
 +----------------+
 2 rows in set (0.00 sec)
 mysql> rename table test to test1;
 Query OK, 0 rows affected (0.05 sec)

 mysql> show tables;
 +----------------+
 | Tables_in_king |
 +----------------+
 | student        |
 | test1          |
 +----------------+
 2 rows in set (0.00 sec)

alter table test1 rename to test；

mysql插入数据解决乱码问题

1. set names 库的字符集，这种方法是临时的每次进来之前都需要执行
2. source test.sql在这个文件中插入set names 库字符集
3. 对已有数据，需要把数据导出去，重新建库建表，在导进来。

创建/查看/删除mysql系统的用户

语法：

1. create user '用户名'@'主机名' identified by '用户名';　　                 创建用户
2. select host,user from mysql.user;                                                     查看用户
3. drop user 用户名@'%';注意可以是单或者双引号，但不能不加，删除用户
4. delete from mysql.user where user='用户名'  and host=‘@后面指定的主机名’;

 mysql> create user 'usrabc'@'%' identified by 'usrabc';  #创建usrabc用户
 Query OK,  rows affected (0.49 sec)
 mysql> select host,user from mysql.user;　　　　　　　　　#查看所有用户　　　
 +-----------+--------+
 | host | user |
 +-----------+--------+
 | % | usrabc |
 | localhost | root |
 +-----------+--------+
  rows in set (0.00 sec)
 mysql> drop user usrabc@'%';　　　　　　　　　　　　#删除usrabc用户
 Query OK,  rows affected (0.00 sec)

处理完用户最好刷新一下权限，flush privileges;

创建mysql用户及赋予用户权限

通过help grant 查看帮助，比较常用的创建用户的方法是：CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass'

CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass'
GRANT ALL ON db1.* TO 'jeffrey'@'localhost'　　　　　　　　　　#这俩命令是先用create创建用户，然后在授权
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost'
GRANT USAGE ON *.* TO 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 

通过grant命令创建用户并授权，命令语法：grant all privileges on dbname.* to username@localhost identified by 'passwd';

grant	all privileges	on dbname.*	to username@localhost	identified by 'passwd'
授权命令	对应权限	目标：库和表	用户名和客户端主机	用户密码

 mysql> grant all privileges on king.* to liang@localhost identified by '';
 #创建liang用户，对king库具备所有权限，允许从localhost主机登陆管理数据库，密码是123456.
 Query OK,  rows affected (0.01 sec)
 mysql> flush privileges;
 Query OK,  rows affected (0.96 sec)

 mysql> show grants for liang@localhost;　　　　　　　　#查看权限
 +-------------------------------------------------------------------------------
 -------------------------------+
 | Grants for liang@localhost
                                |
 +-------------------------------------------------------------------------------
 -------------------------------+
 | GRANT USAGE ON *.* TO 'liang'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74
 329105EE4568DDA7DC67ED2CA2AD9' |
 | GRANT ALL PRIVILEGES ON `king`.* TO 'liang'@'localhost'
                                |
 +-------------------------------------------------------------------------------
 -------------------------------+
  rows in set (0.07 sec)

create和grant配合

 mysql> create user zh@localhost identified by '';
 Query OK,  rows affected (0.04 sec)
 mysql> grant all on king.* to zh@localhost;
 Query OK,  rows affected (0.00 sec)
 mysql> flush privileges;
 Query OK,  rows affected (0.00 sec)

授权局域网内主机远程连接数据库grant all privileges on king.* to liang@10.0.0.% identified by '123456';把localhost改为ip就可以了。连接，mysql -uliang -p123456 -h10.0.0.%

 mysql> show grants for zh@localhost;　　　　　　　　#查看zh用户权限
 +-------------------------------------------------------------------------------
 ----------------------------+
 | Grants for zh@localhost
 |
 +-------------------------------------------------------------------------------
 ----------------------------+
 | GRANT USAGE ON *.* TO 'zh'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329
 105EE4568DDA7DC67ED2CA2AD9' |
 | GRANT ALL PRIVILEGES ON `king`.* TO 'zh'@'localhost'
 |
 +-------------------------------------------------------------------------------
 ----------------------------+
  rows in set (0.16 sec)

 mysql> revoke insert on king.* from zh@localhost;　　　　#更改权限
 Query OK,  rows affected (0.04 sec)

 mysql> show grants for zh@localhost;
 +-------------------------------------------------------------------------------
 --------------------------------------------------------------------------------
 -------------------------------------------------------------+
 | Grants for zh@localhost

 |
 +-------------------------------------------------------------------------------
 --------------------------------------------------------------------------------
 -------------------------------------------------------------+
 | GRANT USAGE ON *.* TO 'zh'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329
 105EE4568DDA7DC67ED2CA2AD9'
 |
 | GRANT SELECT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE T
 EMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, A
 LTER ROUTINE, EVENT, TRIGGER ON `king`.* TO 'zh'@'localhost' |
 +-------------------------------------------------------------------------------
 --------------------------------------------------------------------------------
 -------------------------------------------------------------+
  rows in set (0.06 sec)

 mysql -uroot -p123456 -e "show grants for zh@localhost;"|grep -i grant　　#用linux中grep命令过滤需要的权限
 Grants for zh@localhost
 GRANT USAGE ON *.* TO 'zh'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329
 105EE4568DDA7DC67ED2CA2AD9'
 GRANT SELECT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE T
 EMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, A
 LTER ROUTINE, EVENT, TRIGGER ON `king`.* TO 'zh'@'localhost' 

查看mysql的ALL PRIVILEGES权限mysql -uroot -p123456 -e "show grants for zh@localhost;"|grep -i grant|tail -1|tr ‘，’ ‘\n’  >a.txt

我们在授权用户最小的 满足业务需求的权限，而不是一味的授权ALl  PRIVILEGES。