1. MySQL Overview
2. Download and Installation
3. Database Operation
4. Data Table Operation
5. Table Content Operation
MySQL is a relational database management system, developed by the Swedish MySQL AB company, and is currently a product of Oracle. MySQL is one of the most popular relational database management systems. In terms of WEB applications, MySQL is the best RDBMS (Relational Database Management System) application software.
MySQL is a relational database management system. A relational database stores data in different tables instead of placing all data in one large warehouse, which increases speed and flexibility.
The SQL language used by MySQL is the most commonly used standardized language for accessing databases. MySQL software adopts a dual licensing policy and is divided into community version and commercial version. Due to its small size, fast speed, low total cost of ownership, and especially the characteristics of open source, MySQL is generally chosen as the website database for the development of small and medium-sized websites.
Download address:
Unzip and initialize:
If you want MySQL to be installed in the specified directory, then move the decompressed folder to the specified directory, such as: C:\mysql-5.7.18-winx64
MySQL decompressed bin directory There are a lot of executable files under it. If there is no data folder in the C:\mysql-5.7.18-winx64 directory, create an empty data folder and execute the following command to initialize the data:
cd c:\mysql-5.7.18-winx64\bin mysqld --initialize-insecure
Start the service:
# 进入可执行文件目录 cd c:\mysql-5.7.18-winx64\bin # 启动MySQL服务 mysqld
Start the MySQL client and connect to the MySQL service:
Due to the [mysqld --initialize-insecure] command used during initialization, its By default, the password is not set for the root account
# 进入可执行文件目录 cd c:\mysql-5.7.18-winx64\bin # 连接MySQL服务器 mysql -u root -p # 提示请输入密码,直接回车
So far, the MySQL server has been successfully installed and the client can connect. When operating MySQL in the future, you only need to repeat the above steps. Can. However, it is tedious to repeatedly enter the executable file directory in the above steps. If you want to make the operation easier in the future, you can do the following.
Add environment variables and add the MySQL executable file to the environment variables. In this way, when you start the service and connect in the future, just:
# 启动MySQL服务,在终端输入 mysqld # 连接MySQL服务,在终端输入: mysql -u root -p
It solves some problems in one step, but it is not thorough enough, because when executing mysqld to start the MySQL server, the current terminal will be hung. Then you can solve this problem by making some settings:
Make the MySQL service into a windows service.
# 制作MySQL的Windows服务,在终端执行此命令: "c:\mysql-5.7.18-winx64\bin\mysqld" --install # 移除MySQL的Windows服务,在终端执行此命令: "c:\mysql-5.7.18-winx64\bin\mysqld" --remove
After registering as a service, when starting and shutting down the MySQL service in the future, you only need to execute the following commands:
# 启动MySQL服务 net start mysql # 关闭MySQL服务 net stop mysql
Installation:
yum install mysql-server
Server startup:
mysql.server start
Client connection:
连接: mysql -h host -u user -p 常见错误: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2), it means that the MySQL server daemon (Unix) or service (Windows) is not running. 退出: QUIT 或者 Control+D
1. Display database
show databases; 默认数据库: mysql - 用户权限相关数据 test - 用于用户测试数据 information_schema - MySQL本身架构相关数据
2. Create database
# utf-8create database db_name default charset utf8 collate utf8_general_ci; # gbkcreate database db_name default charset gbk collate gbk_chinese_ci;
3. Using database
use db_name; #显示当前使用的数据库中的所有表: show tables;
4. User management
创建用户 create user '用户名'@'IP地址' identified by '密码'; 删除用户 drop user '用户名'@'IP地址'; 修改用户 rename user '用户名'@'IP地址' to '新用户名'@'IP地址';; 修改密码 set password for '用户名'@'IP地址' = Password('新密码') PS:用户权限相关数据保存在mysql数据库的user表中,所以也可以直接对其进行操作(不建议)
5. Authorization management
show grants for '用户'@'IP地址' -- 查看权限grant 权限 on 数据库.表 to '用户'@'IP地址' -- 授权revoke 权限 on 数据库.表 from '用户'@'IP地址' -- 取消权限
Permissions :
all privileges 除grant外的所有权限select 仅查权限select,insert 查和插入权限 ... usage 无访问权限alter 使用alter tablealter routine 使用alter procedure和drop procedurecreate 使用create tablecreate routine 使用create procedurecreate temporary tables 使用create temporary tablescreate user 使用create user、drop user、rename user和revoke all privilegescreate view 使用create viewdelete 使用deletedrop 使用drop tableexecute 使用call和存储过程file 使用select into outfile 和 load data infilegrant option 使用grant 和 revokeindex 使用indexinsert 使用insert lock tables 使用lock tableprocess 使用show full processlistselect 使用select show databases 使用show databases show view 使用show viewupdate 使用update reload 使用flushshutdown 使用mysqladmin shutdown(关闭MySQL) super 使用change master、kill、logs、purge、master和set global。还允许mysqladmin调试登陆replication client 服务器位置的访问replication slave 由复制从属使用
Database:
对于目标数据库以及内部其他: 数据库名.* 数据库中的所有 数据库名.表 指定数据库中的某张表 数据库名.存储过程 指定数据库中的存储过程 *.* 所有数据库
User and IP:
用户名@IP地址 用户只能在该IP下才能访问 用户名@192.168.1.% 用户只能在该IP段下才能访问(通配符%表示任意) 用户名@% 用户可以在任意IP下访问(默认IP地址为%)
Example:
grant all privileges on db1.tb1 TO '用户名'@'IP'grant select on db1.* TO '用户名'@'IP'grant select,insert on *.* TO '用户名'@'IP'revoke select on db1.tb1 from '用户名'@'IP'特殊的: flush privileges,将数据读取到内存中,从而立即生效。
1. Create table
create table 表名( 列名 类型 是否可以为空, 列名 类型 是否可以为空 )engine=innodb default charset=utf8
Whether it is nullable:
null 表示空,非字符串not null - 不可空
Default value:
默认值,创建列时可以指定默认值,当插入数据时如果未主动设置,则自动添加默认值create table tb1( nid int not null defalut 2, num int not null)
Increment:
auto_increment session auto_increment_increment session auto_increment_offset global auto_increment_increment global auto_increment_offset;
Primary key:
auto_increment
Foreign key:
外键,一个特殊的索引,只能是指定内容create table color( nid int not null primary key, name char(16) not null)create table fruit( nid int not null primary key, smt char(32) null , color_id int not null,constraint fk_cc foreign key (color_id) references color(nid) )
2. Delete table
drop table tb_name;
3. Clear the table
delete from tb_name; 只清空内容,主键值未清空,若再次插入,则主键会继续自增truncate table tb_name; 完全清空
4. Modify the table
添加列:alter table 表名 add 列名 类型 删除列:alter table 表名 drop column 列名 修改列: alter table 表名 modify column 列名 类型; -- 类型 alter table 表名 change 原列名 新列名 类型; -- 列名,类型 添加主键: alter table 表名 add primary key(列名); 删除主键: alter table 表名 drop primary key; alter table 表名 modify 列名 int, drop primary key; 添加外键:alter table 从表 add constraint 外键名称(形如:FK_从表_主表) foreign key 从表(外键字段) references 主表(主键字段); 删除外键:alter table 表名 drop foreign key 外键名称 修改默认值:alter table testalter_tbl alter i set default 1000; 删除默认值:alter table testalter_tbl alter i drop default;
5. Basic data types
The data types of MySQL are roughly divided into: numerical value, time and string
Numerical value:
bit[(M)] 二进制位(101001),m表示二进制位的长度(1-64),默认m=1tinyint[(m)] [unsigned] [zerofill] 小整数,数据类型用于保存一些范围的整数数值范围: 有符号: -128 ~ 127. 无符号: 0 ~ 255 特别的: MySQL中无布尔值,使用tinyint(1)构造。int[(m)][unsigned][zerofill] 整数,数据类型用于保存一些范围的整数数值范围: 有符号: -2147483648 ~ 2147483647 无符号: 0 ~ 4294967295 特别的:整数类型中的m仅用于显示,对存储范围无限制。例如: int(5),当插入数据2时,select 时数据显示为: 00002bigint[(m)][unsigned][zerofill] 大整数,数据类型用于保存一些范围的整数数值范围: 有符号: -9223372036854775808 ~ 9223372036854775807 无符号: 0 ~ 18446744073709551615decimal[(m[,d])] [unsigned] [zerofill] 准确的小数值,m是数字总个数(负号不算),d是小数点后个数。 m最大值为65,d最大值为30。 特别的:对于精确数值计算时需要用此类型 decaimal能够存储精确值的原因在于其内部按照字符串存储。FLOAT[(M,D)] [UNSIGNED] [ZEROFILL] 单精度浮点数(非准确小数值),m是数字总个数,d是小数点后个数。 无符号: -3.402823466E+38 to -1.175494351E-38, 0 1.175494351E-38 to 3.402823466E+38 有符号: 0 1.175494351E-38 to 3.402823466E+38 **** 数值越大,越不准确 ****DOUBLE[(M,D)] [UNSIGNED] [ZEROFILL] 双精度浮点数(非准确小数值),m是数字总个数,d是小数点后个数。 无符号: -1.7976931348623157E+308 to -2.2250738585072014E-308 0 2.2250738585072014E-308 to 1.7976931348623157E+308 有符号: 0 2.2250738585072014E-308 to 1.7976931348623157E+308 **** 数值越大,越不准确 ****
Time:
DATE YYYY-MM-DD(1000-01-01/9999-12-31) TIME HH:MM:SS('-838:59:59'/'838:59:59')YEARYYYY(1901/2155)DATETIMEYYYY-MM-DD HH:MM:SS(1000-01-01 00:00:00/9999-12-31 23:59:59 Y)TIMESTAMPYYYYMMDD HHMMSS(1970-01-01 00:00:00/2037 年某时)
String:
char (m) char数据类型用于表示固定长度的字符串,可以包含最多达255个字符。其中m代表字符串的长度。 PS: 即使数据小于m长度,也会占用m长度varchar(m) varchars数据类型用于变长的字符串,可以包含最多达255个字符。其中m代表该数据类型所允许保存的字符串的最大长度,只要长度小于该最大值的字符串都可以被保存在该数据类型中。 注:虽然varchar使用起来较为灵活,但是从整个系统的性能角度来说,char数据类型的处理速度更快,有时甚至可以超出varchar处理速度的50%。因此,用户在设计数据库时应当综合考虑各方面的因素,以求达到最佳的平衡texttext数据类型用于保存变长的大字符串,可以组多到65535 (2**16 − 1)个字符。 mediumtext A TEXT column with a maximum length of 16,777,215 (2**24 − 1) characters. longtext A TEXT column with a maximum length of 4,294,967,295 or 4GB (2**32 − 1) characters.
Others:
enum 枚举类型, An ENUM column can have a maximum of 65,535 distinct elements. (The practical limit is less than 3000.) 示例:CREATE TABLE shirts ( name VARCHAR(40), size ENUM('x-small', 'small', 'medium', 'large', 'x-large') );INSERT INTO shirts (name, size) VALUES ('dress shirt','large'), ('t-shirt','medium'),('polo shirt','small');set集合类型 A SET column can have a maximum of 64 distinct members. 示例:CREATE TABLE myset (col SET('a', 'b', 'c', 'd'));INSERT INTO myset (col) VALUES ('a,d'), ('d,a'), ('a,d,a'), ('a,d,d'), ('d,a,d');
More references:
insert into 表 (列名,列名...) values (值,值,值...)insert into 表 (列名,列名...) values (值,值,值...),(值,值,值...)insert into 表 (列名,列名...) select (列名,列名...) from 表2. Delete
delete from 表delete from 表 where id=1 and name='alex'3 . Change
update 表 set name = 'alex' where id>14. Check
select * from 表select * from 表 where id > 1select nid,name,gender as gg from 表 where id > 15. Others
1 a、条件 2 select * from 表 where id > 1 and name != 'alex' and num = 12; 3 4 select * from 表 where id between 5 and 16; 5 6 select * from 表 where id in (11,22,33) 7 select * from 表 where id not in (11,22,33) 8 select * from 表 where id in (select nid from 表) 9 10 b、通配符11 select * from 表 where name like 'ale%' - ale开头的所有(多个字符串)12 select * from 表 where name like 'ale_' - ale开头的所有(一个字符)13 14 c、限制15 select * from 表 limit 5; - 前5行16 select * from 表 limit 4,5; - 从第4行开始的5行17 select * from 表 limit 5 offset 4 - 从第4行开始的5行18 19 d、排序20 select * from 表 order by 列 asc - 根据 “列” 从小到大排列21 select * from 表 order by 列 desc - 根据 “列” 从大到小排列22 select * from 表 order by 列1 desc,列2 asc - 根据 “列1” 从大到小排列,如果相同则按列2从小到大排序23 24 e、分组25 select num from 表 group by num26 select num,nid from 表 group by num,nid27 select num,nid from 表 where nid > 10 group by num,nid order nid desc28 select num,nid,count(*),sum(score),max(score),min(score) from 表 group by num,nid29 30 select num from 表 group by num having max(id) > 1031 32 特别的:group by 必须在where之后,order by之前33 34 f、连表35 无对应关系则不显示36 select A.num, A.name, B.name37 from A,B38 Where A.nid = B.nid39 40 无对应关系则不显示41 select A.num, A.name, B.name42 from A inner join B43 on A.nid = B.nid44 45 A表所有显示,如果B中无对应关系,则值为null46 select A.num, A.name, B.name47 from A left join B48 on A.nid = B.nid49 50 B表所有显示,如果B中无对应关系,则值为null51 select A.num, A.name, B.name52 from A right join B53 on A.nid = B.nid54 55 g、组合56 组合,自动处理重合57 select nickname58 from A59 union60 select name61 from B62 63 组合,不处理重合64 select nickname65 from A66 union all67 select name68 from B
References: 1. 2.
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