MySQL常用命令基础操作

Posted 2021-01-17 浪漫De刺猬❥(^_-)

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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[email protected]s->
PROMPT set to ‘[email protected]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=\[email protected]s->

登陆mysql

[root @king~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 2
Server version: 5.5.40 MySQL Community Server (GPL)
Copyright (c) 2000, 2014, 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

1 mysql> update user set password=password(‘123456‘) where user=‘root‘ and host=‘localhost‘;  #password（‘12345‘）是指定一个函数
2 Query OK, 1 row affected (0.00 sec)
3 Rows matched: 1  Changed: 1  Warnings: 0
4 mysql> flush privileges;　　　　　　　　　　　　　　#刷新，没刷新前是在内存里面
5 Query OK, 0 rows affected (0.17 sec)
6 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/3306/my.cnf --skip-grant-tables& mysql -u root -p -S /data/3306/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

数据查询语言（DQL（data query language）），作用从表中获取数据，关键字select，
数据操作语言（DMl（data manipulation language））作用处理表中的数据insert ，update，delete
事务处理语言（TPL）关键字begin，commit和 rollback
数据控制语言（DCl）grant（授权）和revoke
数据定义语言（DDl）create和drop在数据库中创建新表或删除表 alter
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

 1 mysql> create database king;
 2 Query OK, 1 row affected (0.01 sec)
 3 
 4 mysql> show databases;
 5 +--------------------+
 6 | Database           |
 7 +--------------------+
 8 | information_schema |
 9 | king               |
10 | mysql              |
11 | performance_schema |
12 | student            |
13 | test               |
14 +--------------------+
15 6 rows in set (0.01 sec)
16 
17 mysql> show create  database kingG
18 *************************** 1. row ***************************
19        Database: king
20 Create Database: CREATE DATABASE `king` /*!40100 DEFAULT CHARACTER SET utf8 */
21 1 row in set (0.00 sec)
22 
23 mysql>

创建一个指定字符集的数据库

1 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。
2 Query OK, 1 row affected (0.01 sec)

删除数据库

drop database <数据库名字>

 1 mysql> drop database test;
 2 Query OK, 1 row affected (0.07 sec)
 3 
 4 mysql> show databases;
 5 +--------------------+
 6 | Database           |
 7 +--------------------+
 8 | information_schema |
 9 | king               |
10 | mysql              |
11 | performance_schema |
12 | student            |
13 +--------------------+
14 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

 1 mysql> use king;
 2 Database changed
 3 mysql> select database();   #查看当前的数据库，带（）相当于函数，
 4 +------------+
 5 | database() |
 6 +------------+
 7 | king       |
 8 +------------+
 9 1 row in set (0.00 sec)

查看数据库

select database （）;相当于linux下的pwd

 1 mysql> select version();　　　　#查看当前的版本
 2 +-----------+
 3 | version() |
 4 +-----------+
 5 | 5.5.40    |
 6 +-----------+
 7 1 row in set (0.06 sec)
 8 mysql> select user();　　　　　　#查看当前的用户
 9 +----------------+
10 | user()         |
11 +----------------+
12 | [email protected] |
13 +----------------+
14 1 row in set (0.04 sec)
15 mysql> select now();　　　　　　#查看当前的时间
16 +---------------------+
17 | now()               |
18 +---------------------+
19 | 2018-11-02 19:26:39 |
20 +---------------------+
21 1 row in set (0.02 sec)
22 mysql>

表操作

创建表并查看

create table <表名>（<字段名1><类型1>）;

 1 mysql> create table im(id int(3) not null, name varchar(20) not null default‘QQ‘　　　　#创建表id为int类型，name为varchar
 2 );
 3 Query OK, 0 rows affected (0.59 sec)
 4 mysql> show tables from king;　　　　　　　　　　　　　　#从king数据库中查看表
 5 +----------------+
 6 | Tables_in_king |
 7 +----------------+
 8 | im |
 9 +----------------+
10 1 row in set (0.04 sec)
11 mysql> desc im;　　　　　　　　　　　　　　　　　　　　#查看表结构
12 +-------+-------------+------+-----+---------+-------+
13 | Field | Type | Null | Key | Default | Extra |
14 +-------+-------------+------+-----+---------+-------+
15 | id | int(3) | NO | | NULL | |
16 | name | varchar(20) | NO | | QQ | |
17 +-------+-------------+------+-----+---------+-------+
18 2 rows in set (0.22 sec)
19 mysql>

show colums from im;查看表结构

1 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
2 *************************** 1. row ***************************
3        Table: im
4 Create Table: CREATE TABLE `im` (
5   `id` int(3) NOT NULL,
6   `name` varchar(20) NOT NULL DEFAULT ‘QQ‘
7 ) ENGINE=InnoDB DEFAULT CHARSET=utf8
8 1 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));

1 mysql> create table student( id int (4) not null auto_increment, name char(20) n
2 ot null, age tinyint(2) not null default‘0‘,dept varchar(16) default null,primar
3 y key (id), key index_name(name));
4 Query OK, 0 rows affected (0.18 sec)

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

 1 mysql> desc student;　　　　　　　　#查看创建的student表
 2 +-------+-------------+------+-----+---------+----------------+
 3 | Field | Type        | Null | Key | Default | Extra          |
 4 +-------+-------------+------+-----+---------+----------------+
 5 | id    | int(4)      | NO   | PRI | NULL    | auto_increment |
 6 | name  | char(20)    | NO   | MUL | NULL    |                |
 7 | age   | tinyint(2)  | NO   |     | 0       |                |
 8 | dept  | varchar(16) | YES  |     | NULL    |                |
 9 +-------+-------------+------+-----+---------+----------------+
10 4 rows in set (0.17 sec)

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

1 mysql> alter table student drop  primary key ;
2 ERROR 1075 (42000): 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

 1 mysql> show index from studentG;
 2 *************************** 1. row ***************************
 3         Table: student
 4    Non_unique: 0
 5      Key_name: PRIMARY
 6  Seq_in_index: 1
 7   Column_name: id
 8     Collation: A
 9   Cardinality: 0
10      Sub_part: NULL
11        Packed: NULL
12          Null:
13    Index_type: BTREE
14       Comment:
15 Index_comment:
16 *************************** 2. row ***************************
17         Table: student
18    Non_unique: 1
19      Key_name: index_name
20  Seq_in_index: 1
21   Column_name: name
22     Collation: A
23   Cardinality: 0
24      Sub_part: NULL
25        Packed: NULL
26          Null:
27    Index_type: BTREE
28       Comment:
29 Index_comment:
30 2 rows in set (0.00 sec)

创建唯一索引

create unique index uni on student（name）;

 1 mysql> create unique index uni on student (name);
 2 Query OK, 0 rows affected (0.09 sec)
 3 Records: 0  Duplicates: 0  Warnings: 0
 4 mysql> desc student;
 5 +-------+-------------+------+-----+---------+----------------+
 6 | Field | Type        | Null | Key | Default | Extra          |
 7 +-------+-------------+------+-----+---------+----------------+
 8 | id    | int(4)      | NO   | PRI | NULL    | auto_increment |
 9 | name  | char(20)    | NO   | UNI | NULL    |                |
10 | age   | tinyint(2)  | NO   |     | 0       |                |
11 | dept  | varchar(16) | YES  |     | NULL    |                |
12 +-------+-------------+------+-----+---------+----------------+
13 4 rows in set (0.02 sec)

要在表的列上创建索引
索引会加快查询的速度，但是会影响更新的速度
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
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)

);

 1 mysql> create table test(id int(4) not null auto_increment, name char(20) not n
 2 ll,primary key (id));
 3 Query OK, 0 rows affected (0.01 sec)
 4 mysql> show tables;
 5 +----------------+
 6 | Tables_in_king |
 7 +----------------+
 8 | student        |
 9 | test           |
10 +----------------+
11 2 rows in set (0.00 sec)
12 mysql> insert into test (id,name) values(1,‘boy‘);  #插入数据，主键自增我们直接插name，insert into test（name） values（‘new‘）;
13 Query OK, 1 row affected (0.05 sec)
14 mysql> select *from test;
15 +----+------+
16 | id | name |
17 +----+------+
18 |  1 | boy  |
19 +----+------+
20 1 row in set (0.04 sec)

mysql> delete from test;
Query OK, 1 row affected (0.05 sec)
mysql> select *from test;
Empty set (0.00 sec)
mysql> insert into test (id,name) values(1,‘boy‘),(2,‘new‘);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

Loading....

创建/查看/删除mysql系统的用户

语法：

create user ‘用户名‘@‘主机名‘ identified by ‘用户名‘;　　创建用户
select host,user from mysql.user; 查看用户
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
delete from mysql.user where user=‘用户名‘ and host=‘@后面指定的主机名’;

 1 mysql> create user ‘usrabc‘@‘%‘ identified by ‘usrabc‘;  #创建usrabc用户
 2 Query OK, 0 rows affected (0.49 sec)
 3 mysql> select host,user from mysql.user;　　　　　　　　　#查看所有用户　　　
 4 +-----------+--------+
 5 | host | user |
 6 +-----------+--------+
 7 | % | usrabc |
 8 | localhost | root |
 9 +-----------+--------+
10 2 rows in set (0.00 sec)
11 mysql> drop user [email protected]‘%‘;　　　　　　　　　　　　#删除usrabc用户
12 Query OK, 0 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 90

通过grant命令创建用户并授权，命令语法：grant all privileges on dbname.* to [email protected] identified by ‘passwd‘;

grant	all privileges	on dbname.*	to [email protected]	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

1 mysql> grant all privileges on king.* to [email protected] identified by ‘123456‘;
2 #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.
3 Query OK, 0 rows affected (0.01 sec)
4 mysql> flush privileges;
5 Query OK, 0 rows affected (0.96 sec)

 1 mysql> show grants for [email protected];　　　　　　　　#查看权限
 2 +-------------------------------------------------------------------------------
 3 -------------------------------+
 4 | Grants for [email protected]
 5                                |
 6 +-------------------------------------------------------------------------------
 7 -------------------------------+
 8 | GRANT USAGE ON *.* TO ‘liang‘@‘localhost‘ IDENTIFIED BY PASSWORD ‘*6BB4837EB74
 9 329105EE4568DDA7DC67ED2CA2AD9‘ |
10 | GRANT ALL PRIVILEGES ON `king`.* TO ‘liang‘@‘localhost‘
11                                |
12 +-------------------------------------------------------------------------------
13 -------------------------------+
14 2 rows in set (0.07 sec)

create和grant配合

1 mysql> create user [email protected] identified by ‘123456‘;
2 Query OK, 0 rows affected (0.04 sec)
3 mysql> grant all on king.* to [email protected];
4 Query OK, 0 rows affected (0.00 sec)
5 mysql> flush privileges;
6 Query OK, 0 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 [email protected]% identified by ‘123456‘;把localhost改为ip就可以了。连接，mysql -uliang -p123456 -h10.0.0.%

 1 mysql> show grants for [email protected];　　　　　　　　#查看zh用户权限
 2 +-------------------------------------------------------------------------------
 3 ----------------------------+
 4 | Grants for [email protected]
 5 |
 6 +-------------------------------------------------------------------------------
 7 ----------------------------+
 8 | GRANT USAGE ON *.* TO ‘zh‘@‘localhost‘ IDENTIFIED BY PASSWORD ‘*6BB4837EB74329
 9 105EE4568DDA7DC67ED2CA2AD9‘ |
10 | GRANT ALL PRIVILEGES ON `king`.* TO ‘zh‘@‘localhost‘
11 |
12 +-------------------------------------------------------------------------------
13 ----------------------------+
14 2 rows in set (0.16 sec)
15 
16 mysql> revoke insert on king.* from [email protected];　　　　#更改权限
17 Query OK, 0 rows affected (0.04 sec)
18 
19 mysql> show grants for [email protected];
20 +-------------------------------------------------------------------------------
21 --------------------------------------------------------------------------------
22 -------------------------------------------------------------+
23 | Grants for [email protected]
24 
25 |
26 +-------------------------------------------------------------------------------
27 --------------------------------------------------------------------------------
28 -------------------------------------------------------------+
29 | GRANT USAGE ON *.* TO ‘zh‘@‘localhost‘ IDENTIFIED BY PASSWORD ‘*6BB4837EB74329
30 105EE4568DDA7DC67ED2CA2AD9‘
31 |
32 | GRANT SELECT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE T
33 EMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, A
34 LTER ROUTINE, EVENT, TRIGGER ON `king`.* TO ‘zh‘@‘localhost‘ |
35 +-------------------------------------------------------------------------------
36 --------------------------------------------------------------------------------
37 -------------------------------------------------------------+
38 2 rows in set (0.06 sec)

1 mysql -uroot -p123456 -e "show grants for [email protected];"|grep -i grant　　#用linux中grep命令过滤需要的权限
2 Grants for [email protected]
3 GRANT USAGE ON *.* TO ‘zh‘@‘localhost‘ IDENTIFIED BY PASSWORD ‘*6BB4837EB74329
4 105EE4568DDA7DC67ED2CA2AD9‘
5 GRANT SELECT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE T
6 EMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, A
7 LTER ROUTINE, EVENT, TRIGGER ON `king`.* TO ‘zh‘@‘localhost‘

查看mysql的ALL PRIVILEGES权限mysql -uroot -p123456 -e "show grants for [email protected];"|grep -i grant|tail -1|tr ‘，’ ‘ ’ >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。

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