1.安装配置

2.启动mysql服务并配置

    mysql> \s（status也行）

                      查看当前服务器状态

                      查看编码状态

        Server characterset : utf8

        Db characterset: utf8

        Client characterset: gbk

        Conn. characterset: gbk

        修改：---进入配置文件my.ini

        客户端：

            [mysql]

            default-character-set=utf8

        服务端：

            [mysqld]

            character-set-server=utf8

查看状态和修改配置

3.登陆/退出MySql

    登陆：

        常用参数：

        -u, --username=name用户名(注：5.5版本去掉了--username写法)

        -p, 密码

        -h, --host服务器名称

        -P， --port端口号

        -D， --database， 打开指定数据库

        --prompt=name， 设置命令提示符

        --delimiter=name， 指定分隔符

        -V，--version，输出版本信息并且退出

        案例：

        a)mysql -rroot -p

        b)mysql -h127.0.0.1 -uroot -p

        c）mysql -h127.0.0.1 -uroot -p --prompt=abc （只对当前连接有效）

        d)mysql -uroot -proot -V

登陆

    退出：

        exit

        quit

        \q

        Ctrl + c

退出

4.Mysql常用命令：

    显示当前版本 SELECT VERSION();

    显示当前日期时间 SELECT NOW();

    显示当前用户 SELECT USER();

    修改分隔符 DELIMITER \

    开启输出日志 \T +路径

    结束输出日志 \t

运维常用命令

	MYSQL语句规范：

	1.关键字与函数名称全部大写

	2.数据库名称，表名称，字段名称等全部小写

	3.SQL语句必须以分隔符结尾

	4.SQL语句支持折行操作，只要不把单词，标记或引号字符分割为两部分，可以在下一行继续写

	5.数据库名称，表名称，字段名称等尽量不要使用MySQL的保留字，如果需要使用的时候

		需要使用反引号（''）将名称括起来

5.数据库操作：

    a)创建数据库：CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name [[DEFAULT] CHARACTER SET [=] CHARSET_NAME]

                    CREATE DATABASE test CHARACTER SET=UTF8

    b)查看当前服务器下的数据列表: SHOW {DATABASES | SCHEMA}

      得到当前打开的数据库名称 ： SELECT DATABASE();

    c)查看上一步操作产生的警告信息： SHOW WARNINGS;

    d)删除指定数据库 DROP {DATABASE|SCHEMA} [IF EXISTS] db_name

                案例：DROP DATABASE db_aaa1

                      SHOW DATABASES

    e)查看指定数据库的定义 ： SHOW CREATE {DATAASE|SCHEMA} db_name

     f)修改指定数据库的编码方式：ALTER {DATABASE|SCHEMA} db_name [DEFAULT]     CHARACTER SET[=] charset_name

    g)打开指定数据库: USE db_name

创建等语句

6.Mysql中的数据类型  --具体常用的可以参考

    整数类型  --int  --TINYINT(),0为false，其余为true

    浮点类型  --FLOAT 4字节

    字符串类型--CHAR(M)  M 个字节，<=M<=  | VARCHAR(m) <=M<= L+1个字节  | ENUM('value1','value2'..)1或两个字节，取决于枚举值的个数最多65535个值

    日期时间类型 time date datetime  year TIMESTAEP

    二进制类型 视频格式，图片路径啊等
bit[(M)]

            二进制位（），m表示二进制位的长度（-），默认m＝

        tinyint[(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：

                - ～ .

            无符号：

                 ～ 

            特别的： MySQL中无布尔值，使用tinyint()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：

                    - ～

                无符号：

                     ～ 

            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(),当插入数据2时，select 时数据显示为： 

        bigint[(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：

                    - ～

                无符号：

                      ～  

        decimal[(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,

                    1.175494351E-38 to 3.402823466E+38

                有符号：

                    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

                    2.2250738585072014E-308 to 1.7976931348623157E+308

                有符号：

                    2.2250738585072014E-308 to 1.7976931348623157E+308

            **** 数值越大，越不准确 ****

        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

        text

            text数据类型用于保存变长的大字符串，可以组多到65535 (** − )个字符。

        mediumtext

            A TEXT column with a maximum length of ,, (** − ) characters.

        longtext

            A TEXT column with a maximum length of ,,, or 4GB (** − ) characters.

        enum

            枚举类型，

            An ENUM column can have a maximum of , distinct elements. (The practical limit is less than .)

            示例：

                CREATE TABLE shirts (

                    name VARCHAR(),

                    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  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');

        DATE

            YYYY-MM-DD（--/--）

        TIME

            HH:MM:SS（'-838:59:59'/'838:59:59'）

        YEAR

            YYYY（/）

        DATETIME

            YYYY-MM-DD HH:MM:SS（-- ::/-- ::    Y）

        TIMESTAMP

            YYYYMMDD HHMMSS（-- ::/ 年某时）

完整版数据类型

7.（一）数据库表相关操作

a.什么是表？

         数据表是数据库最重要的组成部分之一，是其他对象的基础

         数据表是存储数据的数据结构

         数据表示包含了特定实体类别的数据

         数据表由行（row）和列（column）构成的二维网络

         数据表一定现有表结构，再有数据

         数据表至少有一列，可以没有行或者多行

         数据表名称要求唯一，而且不要包含特殊字符

b.如何创建数据表？

         CREATE TABLE [IF NOT EXISTS] tbl_name(字段名称 字段类型 [完整性约束条件]。。。)ENGINE=引擎名称 CHARSET='编码方式'；

         完整性约束条件：

                         1.PRIMARY KEY主键v--唯一的字段，且不能重复

                         2.AUTO_INCREMENT自增长

                         3.FOREIGN KEY 外键

                         4.NOT NULL 非空

                         5.UNIQUE KEY 唯一

                         6.DEFAULT默认值

c.如何查看数据库中的数据表以及表结构？

 查看数据库下的数据表： SHOW TABLES

 查看指定表的表结构：

 DESC tbl_name

 DESCRIBE tbl_name

 SHOW COLUMNS FROM tbl_name

d.创建表

案例一：创建新闻分类cms_cate 编号，分类名称，分类描述

后加：注意一个地方：create table ....(id int,caption chr注意这里写完就没有逗号了)。。。；否则报错，大爷的找了一晚上。

 CREATE TABLE IF NOT EXISTS cms_cate(

 id TINYINT,

 cateName VARCHAR(50),

 cateDesc VARCHAR(200),

 )ENGINE=MyISAM CHARSET=UTF8;

代码

案例二：
创建新闻表cms_news
编号，新闻标题，新闻内容，新闻发布时间，点击量，是否置顶，新闻所属分类，发布人

 CREATE TABLE Persons

 (

 Id_P int NOT NULL,

 LastName varchar(255) NOT NULL,

 FirstName varchar(255),

 Address varchar(255),

 City varchar(255),

 UNIQUE (Id_P)

 );

代码一

 CREATE TABLE IF NOT EXISTS cms_testnews(

 id INT PRIMARY KEY,

 title VARCHAR(50)  unique not null,

 content TEXT  not null,

 pubTime INT unique not null,

 isTop TINYINT(1) COMMENT '0代表不置顶，1代表置顶'

 ) ENGINE=InnoDB CHARSET=UTF8;

代码二

7.（二）MySQL 存储引擎

a.什么是存储引擎？

         存储引擎就是指表的类型。数据库的存储类型决定了表在计算机中的存储方式。用户可以根据不同的存储方式、是否

         进行事务处理等来选择合适的存储引擎

b.如何查看MySQL的存储引擎？

         查看MySQL支持的存储引擎：       SHOW ENGINES \G;

                         Engine:存储引擎

                         Support：是否支持这种存储引擎

                         Comment：引擎特点

                         Transactions:是否支持事务处理

                         XA：是否是分布式的交易处理

                         Savepoints：是否支持保存点

         查看显示支持的存储引擎信息：    SHOW VARIABLES LIKE 'have%'

         查看默认的存储引擎：            SHOW VARIABLES LIKE 'storage_engine'

c.MySQL常用存储引擎及特点：

                             InnoDB存储引擎  --5.1版本之后

                                             事务修改：---进入配置文件my，回滚，修复，分布式，多版本并发控制的事物安全

                             MyISAM存储引擎  --5.1版本之前

                                             frm --存储表结构

                                             myd     --存储数据

                                             myi --存储索引

                             MEMORY存储引擎

                                             数据存储在内存，安全性低，速度快，生命周期短

d.如何选择合适的存储引擎？

　　　　　　---建议根据需求来选择存储引擎

完整性约束条件：

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" alt="" />

1、给字段选择合适的类型
PRI代表主键 不能为空， 一个表中只能有一个主键

查看创建表的定义

SHOW CREATE TABLE user1；

2、AUTO_INCREMENT自增长
被标志成自增长的一定是主键，主键不一定是自增长的

CREATE TABLE IF NOT EXISTS user5(

id SMALLINT KEY AUTO_INCREMENT,

username VARCHAR()

    );  --）AUTO_INCREMENT=;指定起始值increment(自增长)
INSERT user5 VALUES(,'KING');

　　由于是自增长，可以换种写法

INSERT user5(username) VALUES('QUEN');

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" 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3、NOT NULL非空 --经常配合默认值使用

无符号的UNSIGEND(unsigned)

CREATE TABLE IF NOT EXISTS user7(

id INT UNSIGNED KEY AUTO_INCREMENT, 意思id是无符号的自增长的键

username VARCHAR() NOT NULL,

password CHAR() NOT NULL,

age TINYINT UNSIGNED

    );

INSERT user7(username, passwprd) VALUES('KING', 'KING');

INSERT user7(username, passwprd, age) VALUES('KING', 'KING', );

INSERT user7(username, passwprd) VALUES(NULL, 'KING');

实例

4.DEFAULT默认值

CREATE TABLE IF NOT EXISTS user7(

id INT UNSIGNED KEY AUTO_INCREMENT, 意思id是无符号的自增长的键

username VARCHAR() NOT NULL,

password CHAR() NOT NULL,

age TINYINT UNSIGNED DEFAULT

    );

案例

5.UNIQUE KEY 唯一(一个表中只能有一个主键，但可以有多个唯一)

CREATE TABLE IF NOT EXISTS user9(

id TINYINT UNSIGNED KEY AUTO_INCREMENT,

username VARCHAR() NOT NULL UNIQUE,

card CHAR() UNIQUE

    )

DESC user9 ;

案例

6.外键（后面讲-配合多表查询）

外键，一个特殊的索引，只能是指定内容

可以理解为如果表A的主关键字是表B中的字段，则该字段称为表B的外键，表A称为主表，表B称为从表。外键是用来实现参照完整性的。

            creat table color(

                nid int not null primary key,

                name char() not null

            )

            create table fruit(

                nid int not null primary key,

                smt char() null ,

                color_id int not null,

                constraint fk_cc foreign key (color_id) references color(nid)

            )

案例

如何操作表结构

修改表名：ALTER TABLE tbl_name RENAME [TO|AS] NEW_NAME

        RENAME TABLE tbl_name TO new_name

添加字段:ALTER TABLE tbl_name ADD 字段名称 字段类型【完整性约束条件】[FIRST|AFTER字段名称]

删除字段：ALTER TABLE tbl_name DROP 字段名称

修改字段属性：ALTER TABLE tbl_name MODIFY 字段名称 字段类型【完整性约束条件】【FIRST|AFTER 字段名称】

修改字段名称：ALTER TABLE tbl_name CHANGE 旧字段名称 新字段名称字段类型[完整性约束条件]【FIRST|AFTER字段名称】

添加默认值：ALTER TABLE tbl_name ALTER 字段名称SET DEFAULT默认值

删除默认值：ALTER TABLE tbl_name ALTER 字段名称 DFOP DEFAULT

添加主键：ALTER TABLE tbl_name ADD [CONSTRAINT [symbol]] PRIMARY KEY[index_type] (字段名称，...)

删除主键：ALTER TABLE tbl_name DROP PRIMARY KEY

添加唯一：ALTER TABLE tbl_name ADD [CONSTRAINT[symbol]] UNIQUE [INDEX|KEY] [索引名称](字段名称，..)

删除唯一：ALTER TABLE tbl_name DROP {INDEX|KEY} index_name

修改表的存储引擎：ALTER TABLE tbl_name ENGING=存储引擎名称

设置自增长的值：ALTER TABLE tbl_name AUTO_INCREMENT=值

.如何删除数据表

DROP TABLE[IF EXISTS] tbl_name[,tbl_name....]
CREATE TABLE IF NOT EXISTS user10(

id SMALLINT UNSIGNED KEY AUTO_INCREMENT,

username VARCHAR() NOT NULL UNIQUE,

password CHAR() NOT NULL,

email VARCHAR() NOT NULL DEFAULT '12344@qq.com',

    );

添加字段

以user10为例

添加card字段CHAR();

ALTER TABLE user10 ADD card CHAR();

查看表结构：DESC user10;

完整性约束条件：

ALTER TABLE user10 ADD test VARCHAR() NOT NULL UNIQUE;

ALTER TABLE user10 ADD test1 VARCHAR() NOT NULL FIRST;

ALTER TABLE user10 ADD test2 VARCHAR() NOT NULL DEFAULT  AFTER username;

选中一次表，完成多个操作

ALTER GTABLE user10

ADD test4 INT NOT NULL DEFAULT  AFTER password,

ADD test5 FLOAT(,) FIRST,

ADD test6 SET('A','B','C');

查看表结构：DESC user10;

案例

删除email字段

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" alt="" />

ALTER TABLE user10 DROP test6;

ALTER TABLE user10 DROP test1;

DESC user10;

一次删除多个字段

ALTER TABLE user10

DROP test2,

DROP test3,

....;

案例

添加test字段删除addr字段

ALTER TABLE user10

ADD test  INT UNSIGNED NOT NULL DEFAULT  AFTER sex,

DROP addr;

案例

修改字段属性

ALTER TABLE uer10 MODIFY email VARCHAR();--修改的是所有属性，没写的会变回默认

所以建议在改之前要先DESC tbl_name；查看一下表结构

添加默认值

CREATE TABEL IF NOT EXISTS test12(

id TINYINT UNSIGNED KEY AUTO_INCREMENT,

username VARCHAR() NOT NULL UNIQUE,

age TINYINT UNSIGNED

    );
添加默认值：

ALTER TABLE user11 ALTER age SET DEFAULT ;

DESC user11;

ALTER TABLE user11 ALTER age DROP DEFAULT;

ALTER TABLE user11 ALTER username DROP DEFAULT;

案例

如何添加主键

CREATE TABLE IF NOT EXISTS test12(

id INT

    );

ALTER TABLE test12 ADD PRIMARY KEY(id);

案例

CREATE TABLE IF NOT EXISTS test13(

id INT,

card CHAR(),

username VARCHAR() NOT NULL

    );

ALTER TABLE test13 ADD PRIMARY KEY(id, card);

案例

删除test12表的主键

ALTER TABLE test12 DROP PRIMARY KEY;

在添加回来

ALTER TABLE test12 ADD CONSTRAINT symbol PRIMARY KEY index_type(id);

案例

----注意：

带有主键的自增长---删除

CREATE TABLE IF NOT EXISTS test14(

id INT UNSIGNED KEY AUTO_INCREMENT

    );

ALTER TABLE test14 DROP PRIMARY KEY; ---会报错；所以先删除自增长

所以：

ALTER TABLE test14 MODIFY id INT UNSIGNED;利用MODIFY关键字去掉了特殊属性；（就是利用修改属性，没修改的变成默认值）

ALTER TABLE test14 DROP PRIMARY KEY;

修改表的存储引擎
修改表的存储引擎为MyISAM;

ALTER TABLE user12 ENGINE=MyISAM;

修改自增长的值

ALTER TABLE user12 AUTO_INCREMENT=;

删除数据表

DROP TABLE[IF EXISTS] tbl_name[, tbl_name...]

DROP TABLE IF EXISTS user12;

SHOW WARNINGS;  查看警告

DROP TABLE IF EXISTS user1,user2,user3;

清空自增id

我们的数据库表中经常会使用id自增，但是每次清空表后id并不是从1开始计数，总是接着之前的进行自增，那么解决呢？

使用mysql的truncate命令，用法：truncate table 表名;

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