（补档）mysql基数-数据库操作
mysql数据库操作
目录
DDL操作
1.数据库操作
//创建数据库
//语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME';
[IF NOT EXISTS]
用于判断数据库存不存在，若存在就退出，若不存在就创建
平常可以不加，若数据库太多了，可以使用这个判断
//查看当前实例有哪些数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
//创建数据库xiaodada
mysql> create database if not exists xiaodada;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| xiaodada |
+--------------------+
5 rows in set (0.00 sec)
//删除数据库
//语法：DROP DATABASE [IF EXISTS] 'DB_NAME';
[IF EXISTS]
若不存在就退出，若存在就删除
mysql> drop database xiaodada;
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)
2.表操作
//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';
mysql> create database if not exists xiaodada; //创建数据库xiaodada
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| xiaodada |
+--------------------+
5 rows in set (0.00 sec)
mysql> use xiaodada; //进入数据库
Database changed
mysql> create table linux (id int not null,name varchar(10),age tinyint(3)); //创建linux表
Query OK, 0 rows affected (0.01 sec)
mysql> show tables;
+--------------------+
| Tables_in_xiaodada |
+--------------------+
| linux |
+--------------------+
1 row in set (0.00 sec)
mysql> desc linux; //查看表的结构
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(10) | YES | | NULL | |
| age | tinyint(3) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
//删除表
//语法：DROP TABLE [ IF EXISTS ] 'table_name';
mysql> drop table linux;
Query OK, 0 rows affected (0.00 sec)
mysql> show tables;
Empty set (0.00 sec)
mysql数据类型
MySQL中定义数据字段的类型对数据库的优化是非常重要的。MySQL支持多种类型，大致可以分为三类：数值、日期/时间和字符串(字符)类型。
数值类型
MySQL支持所有标准SQL数值数据类型。这些类型包括严格数值数据类型(INTEGER、SMALLINT、DECIMAL和NUMERIC)，以及近似数值数据类型(FLOAT、REAL和DOUBLE PRECISION)。
关键字INT是INTEGER的同义词，关键字DEC是DECIMAL的同义词。BIT数据类型保存位字段值，并且支持MyISAM、MEMORY、InnoDB和BDB表。作为SQL标准的扩展，MySQL也支持整数类型TINYINT、MEDIUMINT和BIGINT。
下面的表显示了需要的每个整数类型的存储和范围
| 类型 | 大小 | 范围（有符号） | 范围（无符号） | 用途 |
|---|---|---|---|---|
| TINYINT | 1 byte | (-128，127) | (0，255) | 小整数值 |
| SMALLINT | 2 bytes | (-32 768，32 767) | (0，65 535) | 大整数值 |
| MEDIUMINT | 3 bytes | (-8 388 608，8 388 607) | (0，16 777 215) | 大整数值 |
| INT或INTEGER | 4 bytes | (-2 147 483 648，2 147 483 647) | (0，4 294 967 295) | 大整数值 |
| BIGINT | 8 bytes | (-9,223,372,036,854,775,808，9 223 372 036 854 775 807) | (0，18 446744 073 709 551 615) | 极大整数值 |
| FLOAT | 4 bytes | (-3.402 823 466 E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351 E+38) | 0，(1.175 494 351 E-38，3.402 823 466 E+38) | 单精度 浮点数值 |
| DOUBLE | 8 bytes | (-1.797 693 134 862 315 7 E+308，-2.225 073 858 507 201 4 E-308)，0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) | 0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) | 双精度 浮点数值 |
| DECIMAL | 对DECIMAL(M,D) ，如果M>D，为M+2否则为D+2 | 依赖于M和D的值 | 依赖于M和D的值 | 小数值 |
日期和时间类型
表示时间值的日期和时间类型为DATETIME、DATE、TIMESTAMP、TIME和YEAR。每个时间类型有一个有效值范围和一个"零"值，当指定不合法的MySQL不能表示的值时使用"零"值。TIMESTAMP类型有专有的自动更新特性，将在后面描述。
| 类型 | 大小( bytes) | 范围 | 格式 | 用途 |
|---|---|---|---|---|
| DATE | 3 | 1000-01-01/9999-12-31 | YYYY-MM-DD | 日期值 |
| TIME | 3 | '-838:59:59'/'838:59:59' | HH:MM:SS | 时间值或持续时间 |
| YEAR | 1 | 1901/2155 | YYYY | 年份值 |
| DATETIME | 8 | 1000-01-01 00:00:00/9999-12-31 23:59:59 | YYYY-MM-DD HH:MM:SS | 混合日期和时间值 |
| TIMESTAMP | 4 | 1970-01-01 00:00:00/2038 结束时间是第 2147483647 秒，北京时间 2038-1-19 11:14:07，格林尼治时间 2038年1月19日 凌晨 03:14:07 | YYYYMMDD HHMMSS | 混合日期和时间值，时间戳 |
字符串类型
字符串类型指CHAR、VARCHAR、BINARY、VARBINARY、BLOB、TEXT、ENUM和SET。该节描述了这些类型如何工作以及如何在查询中使用这些类型。
| 类型 | 大小 | 用途 |
|---|---|---|
| CHAR | 0-255 bytes | 定长字符串 |
| VARCHAR | 0-65535 bytes | 变长字符串 |
| TINYBLOB | 0-255 bytes | 不超过 255 个字符的二进制字符串 |
| TINYTEXT | 0-255 bytes | 短文本字符串 |
| BLOB | 0-65 535 bytes | 二进制形式的长文本数据 |
| TEXT | 0-65 535 bytes | 长文本数据 |
| MEDIUMBLOB | 0-16 777 215 bytes | 二进制形式的中等长度文本数据 |
| MEDIUMTEXT | 0-16 777 215 bytes | 中等长度文本数据 |
| LONGBLOB | 0-4 294 967 295 bytes | 二进制形式的极大文本数据 |
| LONGTEXT | 0-4 294 967 295 bytes | 极大文本数据 |
3.用户操作
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：
- IP地址，如：172.16.12.129
- 通配符
- %：匹配任意长度的任意字符，常用于设置允许从任何主机登录
- _：匹配任意单个字符
//数据库用户创建
//语法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password'];
//创建tom用户
mysql> create user 'tom'@'localhost' identified by '123456';
Query OK, 0 rows affected (0.00 sec)
mysql> select * from mysql.user\G //查看详细用户表
mysql> exit
Bye
[root@localhost ~]# mysql -utom -p123456
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 22
Server version: 5.7.38 MySQL Community Server (GPL)
Copyright (c) 2000, 2022, Oracle and/or its affiliates.
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 'tom'@'localhost';
Query OK, 0 rows affected (0.02 sec)
4.查看命令show
mysql> show character set; //查看支持的所有字符集
mysql> show engines; //查看当前数据库支持的所有存储引擎
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| xiaodada |
+--------------------+
5 rows in set (0.00 sec)
mysql> show tables from xiaodada; //不进入某数据库而列出其包含的所有表
+--------------------+
| Tables_in_xiaodada |
+--------------------+
| linux |
+--------------------+
1 row in set (0.00 sec)
//查看表结构
//语法：DESC [db_name.]table_name;
mysql> desc xiaodada.linux;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(10) | YES | | NULL | |
| age | tinyint(3) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
//查看某表的创建命令
//语法：SHOW CREATE TABLE table_name;
mysql> show create table xiaodada.linux;
+-------+--------------------------------------------------------------+
| Table | Create Table |
+-------+--------------------------------------------------------------+
| linux | CREATE TABLE `linux` (
`id` int(11) NOT NULL,
`name` varchar(10) DEFAULT NULL,
`age` tinyint(3) 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 xiaodada;
Database changed
mysql> show table status like 'linux'\G
*************************** 1. row ***************************
Name: linux
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: 2022-07-25 16:18:01
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
5.获取帮助
//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
DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。
1.INSERT增
//DML操作之增操作insert
//语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...
mysql> insert into dada (id,name,age) value (1,'dom',20);
Query OK, 1 row affected (0.01 sec)
mysql> insert into dada (id,name,age) values (2,'jerry',23),(3,'tom',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',null);
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
2.SELECT语句
字段column表示法
| 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 |
条件判断语句WHERE
| 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：排序，默认为升序（ASC）
| 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];
//查dada这个表的所有字段
mysql> select * from dada;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)
//查dada这张表的name字段
mysql> select name from dada;
+-----------+
| name |
+-----------+
| dom |
| jerry |
| tom |
| sean |
| zhangshan |
| zhangshan |
| lisi |
+-----------+
7 rows in set (0.00 sec)
//以age字段升序排序查dada这张表
mysql> select * from dada order by age;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 7 | lisi | NULL |
| 1 | dom | 20 |
| 6 | zhangshan | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 5 | zhangshan | 26 |
| 4 | sean | 28 |
+----+-----------+------+
7 rows in set (0.00 sec)
//以age字段降序排序查dada这张表
mysql> select * from dada order by age desc;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 3 | tom | 25 |
| 2 | jerry | 23 |
| 1 | dom | 20 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)
//以age这张表升序排序并之取前2个结果查dada这张表
mysql> select * from dada order by age limit 2;
+----+------+------+
| id | name | age |
+----+------+------+
| 7 | lisi | NULL |
| 1 | dom | 20 |
+----+------+------+
2 rows in set (0.00 sec)
//以age这张表降序排序并之取前2个结果查dada这张表
mysql> select * from dada order by age desc limit 2;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
+----+-----------+------+
2 rows in set (0.00 sec)
//以age这张表升序排序并略过第一个结果之取后面2个结果查dada这张表
mysql> select * from dada order by age limit 1,2;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 6 | zhangshan | 20 |
+----+-----------+------+
2 rows in set (0.00 sec)
//判断age字段大于等于25查dada这张表
mysql> select * from dada where age >= 25;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
+----+-----------+------+
3 rows in set (0.00 sec)
//判断age字段大于等于25且name字段为zhangshan查dada这张表
mysql> select * from dada where age >= 25 and name = 'zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
+----+-----------+------+
1 row in set (0.00 sec)
//判断age字段不是null查dada这张表
mysql> select * from dada where age is not null;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
+----+-----------+------+
6 rows in set (0.00 sec)
//判断age字段是null查dada这张表
mysql> select * from dada where age is null;
+----+------+------+
| id | name | age |
+----+------+------+
| 7 | lisi | NULL |
+----+------+------+
1 row in set (0.00 sec)
3.update语句
//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 dada;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)
//将name为lisi字段的age改为30
mysql> update dada set age = 30 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from dada where name = 'lisi';
+----+------+------+
| id | name | age |
+----+------+------+
| 7 | lisi | 30 |
+----+------+------+
1 row in set (0.00 sec)
4.delete语句
//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 dada;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | 30 |
+----+-----------+------+
7 rows in set (0.00 sec)
//删除age字段小于25
mysql> delete from dada where age < 25;
Query OK, 3 rows affected (0.00 sec)
mysql> select * from dada;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 7 | lisi | 30 |
+----+-----------+------+
4 rows in set (0.00 sec)
mysql> delete from dada;
Query OK, 4 rows affected (0.00 sec)
//删除整张表内容
mysql> select * from dada;
Empty set (0.00 sec)
mysql> desc dada;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> delete from dada;
Query OK, 4 rows affected (0.00 sec)
mysql> select * from dada;
Empty set (0.00 sec)
mysql> desc dada;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
5.truncate语句
| 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 |
mysql> select * from dada;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | dom | 20 |
| 2 | jerry | 23 |
| 3 | tom | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)
mysql> truncate dada;
Query OK, 0 rows affected (0.01 sec)
mysql> select * from dada;
Empty set (0.00 sec)
mysql> desc dada;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
DCL操作
创建授权grant
权限类型(priv_type)
| 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 |
指定要操作的对象db_name.table_name
| 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。
语法：
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 |
| daxinyu |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
//授权tom用户在数据库本机上登录访问所有数据库
mysql> grant all on *.* to 'tom'@'localhost' identified by '123456';
Query OK, 0 rows affected, 1 warning (0.00 sec)
//也可表示为：
mysql> grant all on *.* to 'tom'@'127.0.0.1' identified by '123456';
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权tom用户在192.168.118.137上远程登录访问daxinyu数据库
mysql> grant all on daxinyu.* to 'tom'@'192.168.118.137' identified by '123456';
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权tom用户在所有位置上远程登录访问daxinyu数据库
mysql> grant all on daxinyu.* to 'tom'@'%' identified by '123456';
Query OK, 0 rows affected, 1 warning (0.00 sec)
授权后利用student（图形化数据库）进行连接
查看授权
//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tom的授权信息
mysql> show grants for tom;
+--------------------------------------------------+
| Grants for tom@% |
+--------------------------------------------------+
| GRANT USAGE ON *.* TO 'tom'@'%' |
| GRANT ALL PRIVILEGES ON `daxinyu`.* TO 'tom'@'%' |
+--------------------------------------------------+
2 rows in set (0.01 sec)
mysql> show grants for 'tom'@'localhost';
+--------------------------------------------------+
| Grants for tom@localhost |
+--------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'tom'@'localhost' |
+--------------------------------------------------+
1 row in set (0.00 sec)
mysql> show grants for 'tom'@'127.0.0.1';
+--------------------------------------------------+
| Grants for tom@127.0.0.1 |
+--------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'tom'@'127.0.0.1' |
+--------------------------------------------------+
1 row in set (0.00 sec)
取消授权
//语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';
mysql> show grants for 'tom'@'192.168.118.137';
+----------------------------------------------------------------+
| Grants for tom@192.168.118.137 |
+----------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'tom'@'192.168.118.137' |
| GRANT ALL PRIVILEGES ON `dada`.* TO 'tom'@'192.168.118.137' |
| GRANT ALL PRIVILEGES ON `daxinyu`.* TO 'tom'@'192.168.118.137' |
+----------------------------------------------------------------+
3 rows in set (0.00 sec)
mysql> revoke all on dada.* from 'tom'@'192.168.118.137';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for 'tom'@'192.168.118.137';
+----------------------------------------------------------------+
| Grants for tom@192.168.118.137 |
+----------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'tom'@'192.168.118.137' |
| GRANT ALL PRIVILEGES ON `daxinyu`.* TO 'tom'@'192.168.118.137' |
+----------------------------------------------------------------+
2 rows in set (0.00 sec)
实战案例
1.搭建mysql服务
[root@localhost ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm
[root@localhost ~]# rpm -Uvh mysql57-community-release-el7-11.noarch.rpm
[root@localhost ~]# yum module disable mysql
[root@localhost ~]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel --nogpgcheck
[root@localhost ~]# rpm -e mysql57-community-release
[root@localhost ~]# systemctl enable --now mysqld
[root@localhost ~]# grep "password" /var/log/mysqld.log
2022-07-26T04:20:43.787728Z 1 [Note] A temporary password is generated for root@localhost: QthCgNq#g98;
[root@localhost ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.39
Copyright (c) 2000, 2022, Oracle and/or its affiliates.
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> 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> set password = password('123456');
[root@localhost ~]# mysql -uroot -p123456
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 10
Server version: 5.7.39 MySQL Community Server (GPL)
Copyright (c) 2000, 2022, Oracle and/or its affiliates.
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>
2.创建一个以你名字为名的数据库，并创建一张表student，该表包含三个字段（id，name，age），表结构如下：
mysql> desc student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
mysql> create database if not exists daxinyu;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| daxinyu |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> use daxinyu;
Database changed
mysql> create table student (id int(11) not null key auto_increment,name varchar(100) not null,age tinyint(4));
Query OK, 0 rows affected (0.00 sec)
mysql> desc student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
3.查看下该新建的表有无内容（用select语句）
mysql> select * from student;
Empty set (0.00 sec)
4.往新建的student表中插入数据（用insert语句），结果应如下所示：
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
mysql> insert into student (id,name,age) value (1,'tom',20);
Query OK, 1 row affected (0.00 sec)
mysql> insert into student (id,name,age) values (2,'jerry',23),(3,'wangqing',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',null),(8,'chenshuo',10),(9,'wangwu',3),(10,'qiuyi',15),(11,'qiuxiaotian',20);
Query OK, 10 rows affected (0.00 sec)
Records: 10 Duplicates: 0 Warnings: 0
mysql> select * from student;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
11 rows in set (0.00 sec)
5.修改lisi的年龄为50
mysql> update student set age = 50 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student where name = 'lisi';
+----+------+------+
| id | name | age |
+----+------+------+
| 7 | lisi | 50 |
+----+------+------+
1 row in set (0.00 sec)
6.以age字段降序排序
mysql> select * from student order by age desc;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 7 | lisi | 50 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 3 | wangqing | 25 |
| 2 | jerry | 23 |
| 1 | tom | 20 |
| 6 | zhangshan | 20 |
| 11 | qiuxiaotian | 20 |
| 10 | qiuyi | 15 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
+----+-------------+------+
11 rows in set (0.00 sec)
7.查询student表中年龄最小的3位同学跳过前2位
mysql> select * from student order by age limit 2,3;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 10 | qiuyi | 15 |
| 1 | tom | 20 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
3 rows in set (0.00 sec)
8.查询student表中年龄最大的4位同学
mysql> select * from student order by age desc limit 4;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 7 | lisi | 50 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 3 | wangqing | 25 |
+----+-----------+------+
4 rows in set (0.00 sec)
9.查询student表中名字叫zhangshan的记录
mysql> select * from student where name = 'zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
+----+-----------+------+
2 rows in set (0.00 sec)
10.查询student表中名字叫zhangshan且年龄大于20岁的记录
mysql> select * from student where age > 20 and name = 'zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
+----+-----------+------+
1 row in set (0.00 sec)
11.查询student表中年龄在23到30之间的记录
mysql> select * from student where age > 23 and age < 30;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
+----+-----------+------+
3 rows in set (0.00 sec)
12.修改wangwu的年龄为100
mysql> update student set age = 100 where name = 'wangwu';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student where name = 'wangwu';
+----+--------+------+
| id | name | age |
+----+--------+------+
| 9 | wangwu | 100 |
+----+--------+------+
1 row in set (0.00 sec)
13.删除student中名字叫zhangshan且年龄小于等于20的记录
mysql> delete from student where name = 'zhangshan';
Query OK, 2 rows affected (0.00 sec)
mysql> delete from student where age <= 20;
Query OK, 4 rows affected (0.00 sec)
mysql> select * from student;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 7 | lisi | 50 |
| 9 | wangwu | 100 |
+----+----------+------+
5 rows in set (0.00 sec)
