时间：2021-07-01 10:21:17 帮助过：11人阅读
//启动mysql
[root@20liuzhenchao ~]# systemctl start mysqld
[root@20liuzhenchao ~]# systemctl status mysqld
● mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: active (running) since 一 2019-04-22 14:18:23 CST; 1min 29s ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 13899 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Process: 13823 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 13902 (mysqld)
CGroup: /system.slice/mysqld.service
└─13902 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
4月 22 14:18:19 20liuzhenchao systemd[1]: Starting MySQL Server...
4月 22 14:18:23 20liuzhenchao systemd[1]: Started MySQL Server.
//确保3306端口已经监听起来
[root@20liuzhenchao ~]# ss -antl |grep 3306
LISTEN 0 80 :::3306 :::*
//在日志文件中找出临时密码
[root@20liuzhenchao ~]# grep "password" /var/log/mysqld.log
2019-04-22T06:18:21.008637Z 1 [Note] A temporary password is generated for root@localhost: LIUPk=c3)Tp<
//此处的临时密码为LIUPk=c3)Tp<
//使用获取到的临时密码登录mysql
[root@20liuzhenchao ~]# mysql -uroot -p
Enter password: //此处输入密码，可以直接复制你的密码粘贴至此处，也可手动输入
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.25
Copyright (c) 2000, 2019, 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> //看到有这样的标识符则表示成功登录了
//修改mysql登录密码
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)
mysql> ALTER USER ‘root‘@‘localhost‘ IDENTIFIED BY ‘123456‘;
Query OK, 0 rows affected (0.01 sec)
mysql> quit
Bye
//为避免mysql自动升级，这里需要卸载最开始安装的yum源
[root@20liuzhenchao ~]# rpm -qa |grep mysql
mysql-community-devel-5.7.25-1.el7.x86_64
mysql-community-libs-5.7.25-1.el7.i686
mysql-community-server-5.7.25-1.el7.x86_64
mysql-community-common-5.7.25-1.el7.x86_64
mysql-community-libs-compat-5.7.25-1.el7.x86_64
mysql-community-common-5.7.25-1.el7.i686
mysql-community-client-5.7.25-1.el7.x86_64
mysql-community-libs-5.7.25-1.el7.x86_64
mysql57-community-release-el7-10.noarch
[root@20liuzhenchao ~]# yum -y remove mysql57-community-release-el7-10.noarch
已加载插件：fastestmirror, product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
正在解决依赖关系
--> 正在检查事务
---> 软件包 mysql57-community-release.noarch.0.el7-10 将被 删除
--> 解决依赖关系完成
安装大小：30 k
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
正在删除 : mysql57-community-release-el7-10.noarch 1/1
Loading mirror speeds from cached hostfile
验证中 : mysql57-community-release-el7-10.noarch 1/1
删除:
mysql57-community-release.noarch 0:el7-10
完毕！//语法：mysql [OPTIONS] [database]
//常用的OPTIONS：
-uUSERNAME //指定用户名，默认为root
-hHOST //指定服务器主机，默认为localhost，推荐使用ip地址
-pPASSWORD //指定用户的密码
-P# //指定数据库监听的端口，这里的#需用实际的端口号代替，如-P3307
-V //查看当前使用的mysql版本
-e //不登录mysql执行sql语句后退出，常用于脚本
[root@20liuzhenchao ~]# mysql -V
mysql Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using EditLine wrapper
[root@20liuzhenchao ~]# mysql -uroot -p123456 -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, 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>
//注意，不推荐直接在命令行里直接用-pPASSWORD的方式登录，而是使用-p选项，然后交互式输入密码
[root@20liuzhenchao ~]# mysql -uroot -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, 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>
[root@20liuzhenchao ~]# mysql -uroot -p -h127.0.0.1 -e ‘SHOW DATABASES;‘
Enter password:
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+| socket类型 | 说明 |
|---|---|
| ip socket | 默认监听在tcp的3306端口，支持远程通信 |
| unix sock | 监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock）仅支持本地通信 server地址只能是：localhost，127.0.0.1 |
//创建数据库
//语法：CREATE DATABASE [IF NOT EXISTS] ‘DB_NAME‘;
//创建数据库liuzhenchao
mysql> CREATE DATABASE IF NOT EXISTS liuzhenchao;
Query OK, 1 row affected (0.00 sec)
//查看当前实例有哪些数据库
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| liuzhenchao |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
//删除数据库
//语法：DROP DATABASE [IF EXISTS] ‘DB_NAME‘;
//删除数据库liuzhenchao
mysql> DROP DATABASE IF EXISTS liuzhenchao;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)//创建表
//语法：CREATE TABLE table_name (col1 datatype 修饰符,col2 datatype 修饰符) ENGINE=‘存储引擎类型‘;
//在数据库liuzhenchao里创建表liu
mysql> CREATE DATABASE liuzhenchao;
//创建数据库liuzhenchao
Query OK, 1 row affected (0.00 sec)
mysql> use liuzhenchao; //进入liuzhenchao数据库
Database changed
mysql> CREATE TABLE liu (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint); //创建liu表
Query OK, 0 rows affected (0.01 sec)
//查看当前数据库有哪些表
mysql> show tables;
+-----------------------+
| Tables_in_liuzhenchao |
+-----------------------+
| liu |
+-----------------------+
1 row in set (0.00 sec)
//删除表
//语法：DROP TABLE [ IF EXISTS ] ‘table_name‘;
//删除表liu
mysql> drop table liu;
Query OK, 0 rows affected (0.01 sec)
mysql> show tables;
Empty set (0.00 sec)mysql用户帐号由两部分组成，如‘USERNAME‘@‘HOST‘，表示此USERNAME只能从此HOST上远程登录 这里（‘USERNAME‘@‘HOST‘）的HOST用于限制此用户可通过哪些主机远程连接mysql程序，其值可为：
//数据库用户创建
//语法：CREATE USER ‘username‘@‘host‘ [IDENTIFIED BY ‘password‘];
//创建数据库用户liuzhenchao
mysql> create user ‘liuzhenchao‘@‘127.0.0.1‘ identified by ‘123456‘;
Query OK, 0 rows affected (0.01 sec)
//使用新创建的用户和密码登录
[root@20liuzhenchao ~]# mysql -uliuzhenchao -p123456 -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, 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>
//删除数据库用户
//语法：DROP USER ‘username‘@‘host‘;
mysql> drop user ‘liuzhenchao‘@‘127.0.0.1‘;
Query OK, 0 rows affected (0.00 sec)mysql> SHOW CHARACTER SET; //查看支持的所有字符集
+----------+---------------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
......
......
mysql> SHOW ENGINES; //查看当前数据库支持的所有存储引擎
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment
| Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and
foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables
| NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
mysql> show databases; //查看数据库信息
+--------------------+
| Database |
+--------------------+
| information_schema |
| liuzhenchao |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> show tables from liuzhenchao;
//不进入某数据库而列出其包含的所有表
+-----------------------+
| Tables_in_liuzhenchao |
+-----------------------+
| liu |
+-----------------------+
1 row in set (0.00 sec)
//查看表结构
//语法：DESC [db_name.]table_name;
mysql> desc liuzhenchao.liu;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(50) | YES | | NULL | |
| phone_numble | varchar(11) | YES | | NULL | |
+--------------+-------------+------+-----+---------+-------+
3 rows in set (0.07 sec)
//查看某表的创建命令
//语法：SHOW CREATE TABLE table_name;
mysql> show create table liuzhenchao.liu;
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| liu | CREATE TABLE `liu` (
`id` int(11) NOT NULL,
`name` varchar(50) DEFAULT NULL,
`phone_numble` varchar(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
//查看某表的状态
//语法：SHOW TABLE STATUS LIKE ‘table_name‘\G
mysql> use liuzhenchao; //进入数据库liuzhenchao
Database changed
mysql> show table status like ‘liu‘\G
//查看liu表的状态
*************************** 1. row ***************************
Name: liu
Engine: InnoDB
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 16384
Max_data_length: 0
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: 2019-04-23 14:45:56
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)//获取命令使用帮助
//语法：HELP keyword;
mysql> HELP CREATE TABLE; //获取创建表的帮助
Name: ‘CREATE TABLE‘
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
[table_options]
[partition_options]
[IGNORE | REPLACE]
[AS] query_expression
......
......DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。
//DML操作之增操作insert
//语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...
mysql> use liuzhenchao;
Database changed
mysql> insert into liu(id,name,phone_numble) value(1,‘tom‘,13297040973);
Query OK, 1 row affected (0.00 sec) //一次插入一条记录
Query OK, 1 row affected (0.01 sec)
mysql> insert into liu values(2,‘jerry‘,33333333333),(3,‘zhen‘,44444444444),(4,‘chao‘,55555555555),(5,‘boss‘,19045045021);
//一次插入多条记录
Query OK, 4 rows affected (0.00 sec)| 表示符 | 代表什么？ |
|---|---|
| * | 所有字段 |
| as | 字段别名，如col1 AS alias1 当表名很长时用别名代替 |
| 操作类型 | 常用操作符 |
|---|---|
| 操作符 | >，<，>=，<=，=，!= BETWEEN column# AND column# LIKE：模糊匹配 RLIKE：基于正则表达式进行模式匹配 IS NOT NULL：非空 IS NULL：空 |
| 条件逻辑操作 | AND OR NOT |
| ORDER BY语句 | 意义 |
|---|---|
| ORDER BY ‘column_name‘ | 根据column_name进行升序排序 |
| ORDER BY ‘column_name‘ DESC | 根据column_name进行降序排序 |
| ORDER BY ’column_name‘ LIMIT 2 | 根据column_name进行升序排序 并只取前2个结果 |
| ORDER BY ‘column_name‘ LIMIT 1,2 | 根据column_name进行升序排序 |
并且略过第1个结果取后面的2个结果
//DML操作之查操作select
//语法：SELECT column1,column2,... FROM table_name [WHERE clause] [ORDER BY ‘column_name‘ [DESC]] [LIMIT [m,]n];
mysql> use liuzhenchao;
Database changed
mysql> select * from liu;
+----+-------+--------------+
| id | name | phone_numble |
+----+-------+--------------+
| 1 | tom | 13297040973 |
| 2 | jerry | 33333333333 |
| 3 | zhen | 44444444444 |
| 4 | chao | 55555555555 |
| 5 | boss | 19045045021 |
+----+-------+--------------+
5 rows in set (0.00 sec)
mysql> select name from liu;
+-------+
| name |
+-------+
| tom |
| jerry |
| zhen |
| chao |
| boss |
+-------+
5 rows in set (0.00 sec)
mysql> alter table liu add column age tinyint(4) not null;
Query OK, 0 rows affected (1.72 sec)
//插入一列age
mysql> desc liuzhenchao.liu;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(50) | YES | | NULL | |
| phone_numble | varchar(11) | YES | | NULL | |
| age | tinyint(4) | NO | | NULL | |
+--------------+-------------+------+-----+---------+-------+
mysql> update liu set age = 23 where id =1;
Query OK, 1 row affected (0.00 sec)
mysql> update liu set age = 30 where id =2;
Query OK, 1 row affected (0.00 sec)
mysql> update liu set age = 60 where id =3;
Query OK, 1 row affected (0.01 sec)
mysql> update liu set age = 80 where id =4;
Query OK, 1 row affected (0.00 sec)
mysql> update liu set age = 12 where id =5;
Query OK, 1 row affected (0.00 sec)
//向age列中分别插入数据
mysql> select * from liu order by age;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 5 | boss | 19045045021 | 12 |
| 1 | tom | 13297040973 | 23 |
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
+----+-------+--------------+-----+
5 rows in set (0.00 sec)
mysql> select * from liu order by age desc;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 4 | chao | 55555555555 | 80 |
| 3 | zhen | 44444444444 | 60 |
| 2 | jerry | 33333333333 | 30 |
| 1 | tom | 13297040973 | 23 |
| 5 | boss | 19045045021 | 12 |
+----+-------+--------------+-----+
5 rows in set (0.00 sec)
//按年龄降序排列
mysql> select * from liu order by age desc limit 2;
+----+------+--------------+-----+
| id | name | phone_numble | age |
+----+------+--------------+-----+
| 4 | chao | 55555555555 | 80 |
| 3 | zhen | 44444444444 | 60 |
+----+------+--------------+-----+
2 rows in set (0.00 sec)
//排列后取前两个数据
mysql> select * from liu order by age desc limit 1,2;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 3 | zhen | 44444444444 | 60 |
| 2 | jerry | 33333333333 | 30 |
+----+-------+--------------+-----+
2 rows in set (0.00 sec)
//跳过第一个数据后取前两个
mysql> select * from liu where age >=30;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
+----+-------+--------------+-----+
3 rows in set (0.00 sec)
mysql> select * from liu where age >=30 and name = ‘zhen‘;
+----+------+--------------+-----+
| id | name | phone_numble | age |
+----+------+--------------+-----+
| 3 | zhen | 44444444444 | 60 |
+----+------+--------------+-----+
1 row in set (0.00 sec)
mysql> select * from liu where age between 10 and 30;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 1 | tom | 13297040973 | 23 |
| 2 | jerry | 33333333333 | 30 |
| 5 | boss | 19045045021 | 12 |
+----+-------+--------------+-----+
3 rows in set (0.00 sec)
mysql> insert into liu(id,phone_numble,age) value(6,13080619342,55);
Query OK, 1 row affected (0.00 sec)
//加入一行name为空的记录
mysql> select * from liu where name is not null;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 1 | tom | 13297040973 | 23 |
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
| 5 | boss | 19045045021 | 12 |
+----+-------+--------------+-----+
5 rows in set (0.00 sec)
mysql> select * from liu where name is null;
+----+------+--------------+-----+
| id | name | phone_numble | age |
+----+------+--------------+-----+
| 6 | NULL | 13080619342 | 55 |
+----+------+--------------+-----+
1 row in set (0.00 sec)//DML操作之改操作update
//语法：UPDATE table_name SET column1 = new_value1[,column2 = new_value2,...] [WHERE clause] [ORDER BY ‘column_name‘ [DESC]] [LIMIT [m,]n];
mysql> select * from liu;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 1 | tom | 13297040973 | 23 |
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
| 5 | boss | 19045045021 | 12 |
| 6 | NULL | 13080619342 | 55 |
+----+-------+--------------+-----+
6 rows in set (0.01 sec)
mysql> update liu set age =40 where id =1;
Query OK, 1 row affected (0.00 sec)
mysql> select * from liu where id =1;
+----+------+--------------+-----+
| id | name | phone_numble | age |
+----+------+--------------+-----+
| 1 | tom | 13297040973 | 40 |
+----+------+--------------+-----+
1 row in set (0.00 sec)//DML操作之删操作delete
//语法：DELETE FROM table_name [WHERE clause] [ORDER BY ‘column_name‘ [DESC]] [LIMIT [m,]n];
mysql> select * from liu;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 1 | tom | 13297040973 | 40 |
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
| 5 | boss | 19045045021 | 12 |
| 6 | NULL | 13080619342 | 55 |
+----+-------+--------------+-----+
6 rows in set (0.00 sec)
mysql> delete from liu where id = 6;
//删除某条记录
Query OK, 1 row affected (0.00 sec)
mysql> select * from liu;
+----+-------+--------------+-----+
| id | name | phone_numble | age |
+----+-------+--------------+-----+
| 1 | tom | 13297040973 | 40 |
| 2 | jerry | 33333333333 | 30 |
| 3 | zhen | 44444444444 | 60 |
| 4 | chao | 55555555555 | 80 |
| 5 | boss | 19045045021 | 12 |
+----+-------+--------------+-----+
5 rows in set (0.00 sec)
mysql> delete from liu;//删除整张表的内容
Query OK, 5 rows affected (0.00 sec)
mysql> select * from liu;
Empty set (0.00 sec)
mysql> desc liu;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(50) | YES | | NULL | |
| phone_numble | varchar(11) | YES | | NULL | |
| age | tinyint(4) | NO | | NULL | |
+--------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)| 语句类型 | 特点 |
|---|---|
| delete | DELETE删除表内容时仅删除内容，但会保留表结构 DELETE语句每次删除一行，并在事务日志中为所删除的每行记录一项 可以通过回滚事务日志恢复数据 非常占用空间 |
| truncate | 删除表中所有数据，且无法恢复 表结构、约束和索引等保持不变，新添加的行计数值重置为初始值 执行速度比DELETE快，且使用的系统和事务日志资源少 通过释放存储表数据所用的数据页来删除数据，并且只在事务日志中记录页的释放 对于有外键约束引用的表，不能使用TRUNCATE TABLE删除数据 不能用于加入了索引视图的表 |
//语法：TRUNCATE table_name;
mysql> select * from liu;
+----+------+--------------+-----+
| id | name | phone_numble | age |
+----+------+--------------+-----+
| 1 | liu | 34343434343 | 32 |
| 2 | zhen | 13329232222 | 43 |
| 3 | chao | 13086024562 | 60 |
+----+------+--------------+-----+
3 rows in set (0.00 sec)
mysql> truncate liu;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from liu;
Empty set (0.00 sec)
mysql> desc liu;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(50) | YES | | NULL | |
| phone_numble | varchar(11) | YES | | NULL | |
| age | tinyint(4) | NO | | NULL | |
+--------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)| 权限类型 | 代表什么？ |
|---|---|
| ALL | 所有权限 |
| SELECT | 读取内容的权限 |
| INSERT | 插入内容的权限 |
| UPDATE | 更新内容的权限 |
| DELETE | 删除内容的权限 |
| 表示方式 | 意义 |
|---|---|
| . | 所有库的所有表 |
| db_name | 指定库的所有表 |
| db_name.table_name | 指定库的指定表 |
WITH GRANT OPTION：被授权的用户可将自己的权限副本转赠给其他用户，说白点就是将自己的权限完全复制给另一个用户。不建议使用。
GRANT priv_type,... ON [object_type] db_name.table_name TO ‘username‘@‘host‘ [IDENTIFIED BY ‘password‘] [WITH GRANT OPTION];
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| liuzhenchao |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
//授权liuzhenchao用户在数据库本机上登录访问所有数据库
mysql> grant all on *.* to ‘liuzhenchao‘@‘localhost‘ identified by ‘123456‘;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> grant all on *.* to ‘liuzhenchao‘@‘127.0.0.1‘ identified by ‘123456‘;
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权liuzhenchao用户在192.168.56.20上远程登录访问liuzhenchao数据库
mysql> grant all on liuzhenchao.* to ‘liuzhenchao‘@‘192.168.56.20‘ identified by ‘123456‘;
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权liuzhenchao用户在所有位置上远程登录访问liuzhenchao数据库
mysql> grant all on *.* to ‘liuzhenchao‘@‘%‘ identified by ‘123456‘;
Query OK, 0 rows affected, 1 warning (0.00 sec)//查看当前登录用户的授权信息
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO ‘root‘@‘localhost‘ WITH GRANT OPTION |
| GRANT PROXY ON ‘‘@‘‘ TO ‘root‘@‘localhost‘ WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
//查看指定用户liuzhenchao的授权信息
mysql> show grants for liuzhenchao;
+--------------------------------------------------+
| Grants for liuzhenchao@% |
+--------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO ‘liuzhenchao‘@‘%‘ |
+--------------------------------------------------+
1 row in set (0.00 sec)
mysql> show grants for ‘liuzhenchao‘@‘localhost‘;
+----------------------------------------------------------+
| Grants for liuzhenchao@localhost |
+----------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO ‘liuzhenchao‘@‘localhost‘ |
+----------------------------------------------------------+
1 row in set (0.00 sec)
mysql> show grants for ‘liuzhenchao‘@‘127.0.0.1‘;
+----------------------------------------------------------+
| Grants for liuzhenchao@127.0.0.1 |
+----------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO ‘liuzhenchao‘@‘127.0.0.1‘ |
+----------------------------------------------------------+
1 row in set (0.00 sec)//语法：REVOKE priv_type,... ON db_name.table_name FROM ‘username‘@‘host‘;
mysql> revoke all on *.* from ‘liuzhenchao‘@‘192.168.56.20‘;
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)mysql基础
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