主键、外键、建表范式、MySQL索引、用户管理-Toy模板网

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1 案例1：主键

1.1 问题

完成如下练习：

练习主键的创建、查看、删除、添加、验证主键
练习复合主键的使用
练习与auto_increment连用的效果

1.2 方案

主键使用规则：

表头值不允许重复，不允许赋NULL值
一个表中只能有一个primary key 表头
多个表头做主键，称为复合主键，必须一起创建和删除
主键标志PRI
主键通常与auto_increment连用
通常把表中唯一标识记录的表头设置为主键[行号表]

1.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：练习主键的创建、查看、删除、添加、验证主键

    //语法格式1
    create  table  库.表（ 表头名 数据类型  primary key  , 表头名  数据类型 , ..... ）;
    //建表
    mysql>  create table db1.t35(
        -> name char(10) , 
        -> hz_id  char(10) primary key  , 
        -> class char(10) 
        -> );
    Query OK, 0 rows affected (0.49 sec)
    //查看表头
    mysql> desc db1.t35;
    +-------+----------+------+-----+---------+-------+
    | Field | Type     | Null | Key | Default | Extra |
    +-------+----------+------+-----+---------+-------+
    | name  | char(10) | YES  |     | NULL    |       |
    | hz_id | char(10) | NO   | PRI | NULL    |       |
    | class | char(10) | YES  |     | NULL    |       |
    +-------+----------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    //语法格式2
    create  table  库.表（ 字段名 类型 , 字段名 类型 , primary key（字段名） ）;
    //建表
    mysql> create table db1.t36(
        -> name char(10) , 
        -> hz_id  char(10) , 
        -> class char(10),
        -> primary key(hz_id)  
        -> );
    Query OK, 0 rows affected (0.39 sec)
    //查看表头
    mysql> desc db1.t36;
    +-------+----------+------+-----+---------+-------+
    | Field | Type     | Null | Key | Default | Extra |
    +-------+----------+------+-----+---------+-------+
    | name  | char(10) | YES  |     | NULL    |       |
    | hz_id | char(10) | NO   | PRI | NULL    |       |
    | class | char(10) | YES  |     | NULL    |       |
    +-------+----------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    //删除主键命令格式
    mysql> alter  table   库.表   drop primary  key ;
    //例子
    mysql>  alter  table db1.t36  drop primary key ;
    Query OK, 0 rows affected (1.00 sec)
    Records: 0  Duplicates: 0  Warnings: 0
    //查看表头
    mysql> desc  db1.t36;
    +-------+----------+------+-----+---------+-------+
    | Field | Type     | Null | Key | Default | Extra |
    +-------+----------+------+-----+---------+-------+
    | name  | char(10) | YES  |     | NULL    |       |
    | hz_id | char(10) | NO   |     | NULL    |       |
    | class | char(10) | YES  |     | NULL    |       |
    +-------+----------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    mysql> 
    //添加主键命令格式
    mysql> alter  table  库.表  add  primary key(表头名);
    //例子
    mysql> alter  table  db1.t36  add  primary key(hz_id);
    mysql> desc db1.t36;
    +-------+----------+------+-----+---------+-------+
    | Field | Type     | Null | Key | Default | Extra |
    +-------+----------+------+-----+---------+-------+
    | name  | char(10) | YES  |     | NULL    |       |
    | hz_id | char(10) | NO   | PRI | NULL    |       |
    | class | char(10) | YES  |     | NULL    |       |
    +-------+----------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    //使用t35表 验证主键约束
    //查看主键表头
    mysql> desc db1.t35;
    +-------+----------+------+-----+---------+-------+
    | Field | Type     | Null | Key | Default | Extra |
    +-------+----------+------+-----+---------+-------+
    | name  | char(10) | YES  |     | NULL    |       |
    | hz_id | char(10) | NO   | PRI | NULL    |       |
    | class | char(10) | YES  |     | NULL    |       |
    +-------+----------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    //插入第1条记录 正常
    mysql> insert into db1.t35  values ("bob","888","nsd2107");
    Query OK, 1 row affected (0.05 sec)
    //空不可以
    mysql> insert into db1.t35  values ("john",null,"nsd2107"); 
    ERROR 1048 (23000): Column 'hz_id' cannot be null
    mysql> 
    //与第1条重复不可以
    mysql> insert into db1.t35  values ("john","888","nsd2107"); 
    ERROR 1062 (23000): Duplicate entry '888' for key 'PRIMARY'
    //不重复也不是null可以
    mysql> insert into db1.t35  values ("john","988","nsd2107"); 
    Query OK, 1 row affected (0.07 sec)
    //查看表记录
    mysql> select  * from db1.t35 ;
    +------+-------+---------+
    | name | hz_id | class   |
    +------+-------+---------+
    | bob  | 888   | nsd2107 |
    | john | 988   | nsd2107 |
    +------+-------+---------+
    2 rows in set (0.00 sec)

步骤二：练习复合主键的使用

    //创建复合主键 表头依次是客户端ip 、服务端口号、访问状态
    mysql> create  table  db1.t39(
    cip   varchar(15) , 
    port  smallint ,  
    status  enum("deny","allow") , 
    primary key(cip,port)
    );
    //插入记录验证
    insert into  db1.t39  values ("1.1.1.1",22,"deny");
    insert into  db1.t39  values ("1.1.1.1",22,"deny"); 同时相同报错
    insert into  db1.t39  values ("1.1.1.1",80,"deny"); 可以
    insert into  db1.t39  values ("2.1.1.1",80,"allow");可以
    //查看记录
    mysql> select  * from db1.t39;
    +---------+------+--------+
    | cip     | port | status |
    +---------+------+--------+
    | 1.1.1.1 |   22 | deny   |
    | 1.1.1.1 |   80 | deny   |
    | 2.1.1.1 |   80 | allow  |
    +---------+------+--------+
    3 rows in set (0.00 sec)
    //删除复合主键
    mysql> alter table  db1.t39 drop primary key;
    Query OK, 3 rows affected (1.10 sec)
    Records: 3  Duplicates: 0  Warnings: 0
    //查看表头
    mysql>  desc  db1.t39;
    +--------+----------------------+------+-----+---------+-------+
    | Field  | Type                 | Null | Key | Default | Extra |
    +--------+----------------------+------+-----+---------+-------+
    | cip    | varchar(15)          | NO   |     | NULL    |       |
    | port   | smallint             | NO   |     | NULL    |       |
    | status | enum('deny','allow') | YES  |     | NULL    |       |
    +--------+----------------------+------+-----+---------+-------+
    3 rows in set (0.00 sec)
    //没有复合主键约束后 ，插入记录不受限制了
    mysql>  insert into db1.t39 values("2.1.1.1",80,"allow");
    Query OK, 1 row affected (0.06 sec)
    mysql> insert into db1.t39 values("2.1.1.1",80,"deny");
    Query OK, 1 row affected (0.08 sec)
    //查看表记录
    mysql> select  * from  db1.t39;
    +---------+------+--------+
    | cip     | port | status |
    +---------+------+--------+
    | 1.1.1.1 |   22 | deny   |
    | 1.1.1.1 |   80 | deny   |
    | 2.1.1.1 |   80 | allow  |
    | 2.1.1.1 |   80 | allow  |
    | 2.1.1.1 |   80 | deny   |
    +---------+------+--------+
    5 rows in set (0.00 sec)
    //添加复合主键时 字段下的数据与主键约束冲突 不允许添加
    mysql> alter table  db1.t39 add primary key(cip,port);
    ERROR 1062 (23000): Duplicate entry '2.1.1.1-80' for key 't39.PRIMARY'
    //删除重复的数据
    mysql> delete from db1.t39 where cip="2.1.1.1";
    Query OK, 3 rows affected (0.05 sec)
    mysql> select  * from  db1.t39;
    +---------+------+--------+
    | cip     | port | status |
    +---------+------+--------+
    | 1.1.1.1 |   22 | deny   |
    | 1.1.1.1 |   80 | deny   |
    +---------+------+--------+
    2 rows in set (0.00 sec)
    //添加复合主键
    mysql> alter table  db1.t39 add primary key(cip,port);
    Query OK, 0 rows affected (0.67 sec)
    Records: 0  Duplicates: 0  Warnings: 0
    //查看表头
    mysql>  desc  db1.t39;
    +--------+----------------------+------+-----+---------+-------+
    | Field  | Type                 | Null | Key | Default | Extra |
    +--------+----------------------+------+-----+---------+-------+
    | cip    | varchar(15)          | NO   | PRI | NULL    |       |
    | port   | smallint             | NO   | PRI | NULL    |       |
    | status | enum('deny','allow') | YES  |     | NULL    |       |
    +--------+----------------------+------+-----+---------+-------+
    3 rows in set (0.00 sec)

步骤三：练习与auto_increment连用的效果

表头设置了auto_increment属性后，

插入记录时，如果不给表头赋值表头通过自加1的计算结果赋值

要想让表头有自增长表头必须有主键设置才可以

查看表结构时在 Extra （额外设置）位置显示

建表时创建有auto_increment 属性的表头。实现的效果如下：

行号姓名班级住址

1 bob nsd2107 bj

2 bob nsd2107 bj

3 bob nsd2107 bj

4 bob nsd2107 bj

1）建表

    mysql> create     table   db1.t38 (
        -> 行号   int   primary key  auto_increment   , 
        -> 姓名   char(10) , 
        -> 班级   char(7) , 
        -> 住址   char(10)
        -> );
    Query OK, 0 rows affected (0.76 sec)
    //查看表头
    mysql> desc db1.t38 ;
    +--------+----------+------+-----+---------+----------------+
    | Field  | Type     | Null | Key | Default | Extra          |
    +--------+----------+------+-----+---------+----------------+
    | 行号   | int      | NO   | PRI | NULL    | auto_increment |
    | 姓名   | char(10) | YES  |     | NULL    |                |
    | 班级   | char(7)  | YES  |     | NULL    |                |
    | 住址   | char(10) | YES  |     | NULL    |                |
    +--------+----------+------+-----+---------+----------------+
    4 rows in set (0.00 sec)
    //插入表记录 不给自增长表头赋值
    mysql> insert  into  db1.t38(姓名,班级,住址)values("bob","nsd2107","bj");
    Query OK, 1 row affected (0.05 sec)
    mysql> insert  into  db1.t38(姓名,班级,住址)values("bob","nsd2107","bj");
    Query OK, 1 row affected (0.04 sec)
    mysql> insert  into  db1.t38(姓名,班级,住址)values("tom","nsd2107","bj");
    Query OK, 1 row affected (0.05 sec)
    //查看表记录
    mysql> select  * from db1.t38;
    +--------+--------+---------+--------+
    | 行号   | 姓名   | 班级    | 住址   |
    +--------+--------+---------+--------+
    |      1 | bob    | nsd2107 | bj     |
    |      2 | bob    | nsd2107 | bj     |
    |      3 | tom    | nsd2107 | bj     |
    +--------+--------+---------+--------+
    3 rows in set (0.00 sec)

自增长使用注意事项

    //给自增长字段的赋值
    mysql> insert  into  db1.t38(行号,姓名,班级,住址)values(5,"lucy","nsd2107","bj");  
    Query OK, 1 row affected (0.26 sec)
    //不赋值后 用最后1条件记录表头的值+1结果赋值
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");  
    Query OK, 1 row affected (0.03 sec)
    //查看记录
    mysql> select  * from db1.t38 ;
    +--------+--------+---------+--------+
    | 行号   | 姓名   | 班级    | 住址   |
    +--------+--------+---------+--------+
    |      1 | bob    | nsd2107 | bj     |
    |      2 | bob    | nsd2107 | bj     |
    |      3 | tom    | nsd2107 | bj     |
    |      5 | lucy   | nsd2107 | bj     |
    |      6 | lucy   | nsd2107 | bj     |
    +--------+--------+---------+--------+
    5 rows in set (0.00 sec)
    //删除所有行
    mysql> delete  from  db1.t38 ；  
    //再添加行 继续行号 而不是从 1 开始 
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");
    //查看记录
    mysql> select  * from db1.t38;
    +--------+--------+---------+--------+
    | 行号   | 姓名   | 班级    | 住址   |
    +--------+--------+---------+--------+
    |      8 | lucy   | nsd2107 | bj     |
    |      9 | lucy   | nsd2107 | bj     |
    |     10 | lucy   | nsd2107 | bj     |
    +--------+--------+---------+--------+
    3 rows in set (0.01 sec)
    //truncate删除行 再添加行 从1开始
    mysql> truncate table  db1.t38;  
    Query OK, 0 rows affected (2.66 sec)
    //插入记录
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");
    Query OK, 1 row affected (0.04 sec)
    mysql> insert  into  db1.t38(姓名,班级,住址)values("lucy","nsd2107","bj");
    Query OK, 1 row affected (0.30 sec)
    //查看记录
    mysql> select  * from db1.t38;
    +--------+--------+---------+--------+
    | 行号   | 姓名   | 班级    | 住址   |
    +--------+--------+---------+--------+
    |      1 | lucy   | nsd2107 | bj     |
    |      2 | lucy   | nsd2107 | bj     |
    +--------+--------+---------+--------+
    2 rows in set (0.01 sec)
    mysql>

2 案例2：外键

2.1 问题

完成如下练习：

练习外键的创建、查看、删除、添加
验证外键功能

2.2 方案

外键使用规则：

表存储引擎必须是innodb
表头数据类型要一致
被参照表头必须要是索引类型的一种(primary key)

作用：

插入记录时，表头值在另一个表的表头值范围内选择。

2.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：练习外键的创建、查看、删除、添加

//创建外键命令

    create table   库.表(
    表头列表 , 
    foreign key(表头名)        #指定外键
    references 库.表(表头名)   #指定参考的表头名
    on update  cascade         #同步更新
    on  delete  cascade        #同步删除
    )engine=innodb;

需求：仅给公司里已经入职的员工发工资

首先创建存储员工信息的员工表

表名 yg

员工编号 yg_id

姓名 name

    #创建员工表
    create table  db1.yg (
    yg_id   int  primary key  auto_increment , 
    name  char(16) 
    ) engine=innodb;

创建工资表

表名 gz

员工编号 gz_id

工资 pay

    #创建工资表 指定外键表头
    mysql> create table db1.gz(
      gz_id int , pay  float,
    foreign key(gz_id)  references db1.yg(yg_id)
    on update cascade  on delete cascade
    )engine=innodb ;
    //查看工资表外键
    mysql> show create  table db1.gz \G
    *************************** 1. row ***************************
           Table: gz
    Create Table: CREATE TABLE `gz` (
      `gz_id` int(11) DEFAULT NULL,
      `pay` float DEFAULT NULL,
      KEY `gz_id` (`gz_id`),
      CONSTRAINT `gz_ibfk_1` FOREIGN KEY (`gz_id`) REFERENCES `yg` (`yg_id`) ON DELETE CASCADE ON UPDATE CASCADE
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1
    //删除外键
    mysql> alter table db1.gz drop FOREIGN KEY  gz_ibfk_1;
    //查看不到外键
    mysql> show create  table db1.gz \G
    *************************** 1. row ***************************
           Table: gz
    Create Table: CREATE TABLE `gz` (
      `gz_id` int(11) DEFAULT NULL,
      `pay` float DEFAULT NULL,
      KEY `gz_id` (`gz_id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1
    1 row in set (0.00 sec)
    mysql> 
    //添加外键
    mysql> alter table db1.gz 
    add  foreign key(gz_id)  references db1.yg(yg_id)  
    on update cascade  on delete cascade ;
    //查看外键
    mysql> show create  table db1.gz \G
    *************************** 1. row ***************************
           Table: gz
    Create Table: CREATE TABLE `gz` (
      `gz_id` int(11) DEFAULT NULL,
      `pay` float DEFAULT NULL,
      KEY `gz_id` (`gz_id`),
      CONSTRAINT `gz_ibfk_1` FOREIGN KEY (`gz_id`) REFERENCES `yg` (`yg_id`) ON DELETE CASCADE ON UPDATE CASCADE
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1
    1 row in set (0.00 sec)

步骤二：验证外键功能

外键字段的值必须在参考表字段值范围内
验证同步更新（ on update cascade)
验证同步删除（ on delete cascade)

1)、外键字段的值必须在参考表字段值范围内

    员工表插入记录
    mysql> insert into db1.yg (name) values ("jerry"),("tom");
    mysql> select  * from db1.yg;
    工资表插入记录
    mysql> insert into db1.gz values(1,50000);
    mysql> insert into db1.gz values(2,60000);
    mysql> select  * from db1.gz;
    +-------+----------+
    | gz_id | pay      |
    +-------+----------+
    |     1 | 50000    |
    |     2 | 60000    |
    +-------+----------+
    2 rows in set (0.00 sec)
    #没有的3号员工 工资表插入记录报错
    mysql> insert into db1.gz values(3,50000);  
    ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`db1`.`gz`, CONSTRAINT `gz_ibfk_1` FOREIGN KEY (`gz_id`) REFERENCES `yg` (`yg_id`) ON DELETE CASCADE ON UPDATE CASCADE)
    员工表 插入编号3的员工
    mysql> insert into db1.yg (name) values ("Lucy"); 
    mysql> select  * from  db1.yg;  
        可以给3号员工 发工资了 
    mysql> insert into db1.gz values(3,40000);

2)、验证同步更新（ on update cascade)

    查看员工表记录
    mysql> select * from db1.yg;
    +-------+-------+
    | yg_id | name  |
    +-------+-------+
    |     1 | jerry |
    |     2 | tom   |
    |     3 | lucy  |
    +-------+-------+
    3 rows in set (0.00 sec)
    把yg表里编号是3的改成9 
    mysql> update db1.yg set yg_id=9 where yg_id=3;  
    mysql> select * from db1.yg;
    +-------+-------+
    | yg_id | name  |
    +-------+-------+
    |     1 | jerry |
    |     2 | tom   |
    |     9 | lucy  |
    +-------+-------+
    3 rows in set (0.00 sec)
    工资表里编号是3的自动变成 9 
    mysql> select * from db1.gz;
    +-------+----------+
    | gz_id | pay      |
    +-------+----------+
    |     1 | 50000.00 |
    |     2 | 60000.00 |
    |     9 | 40000.00 |
    +-------+----------+
    3 rows in set (0.00 sec)
    mysql>

3)、验证同步删除（ on delete cascade)

    删除前查看员工表记录
    mysql> select * from db1.yg;  
    +-------+-------+
    | yg_id | name  |
    +-------+-------+
    |     1 | jerry |
    |     2 | tom   |
    |     9 | lucy  |
    +-------+-------+
    3 rows in set (0.00 sec)
    删除编号2的员工
    mysql> delete from db1.yg where yg_id=2; 
    Query OK, 1 row affected (0.04 sec)
    删除后查看
    mysql> select * from db1.yg; 
    +-------+-------+
    | yg_id | name  |
    +-------+-------+
    |     1 | jerry |
    |     9 | lucy  |
    +-------+-------+
    2 rows in set (0.00 sec)
    查看工资表也没有编号2的工资了
    mysql> select * from db1.gz;  
    +-------+----------+
    | gz_id | pay      |
    +-------+----------+
    |     1 | 50000     |
    |     9 | 40000     |
    +-------+----------+
    2 rows in set (0.00 sec)
    mysql>

4)、外键使用注意事项

    #被参考的表不能删除
    mysql> drop table db1.yg;
    ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails
    mysql> 
    给gz表的gz_id表头 加主键标签
    保证每个员工只能发1遍工资  且有员工编号的员工才能发工资
    # 如果重复发工资和没有编号的发了工资 删除记录后 再添加主键 
    delete form db1.gz;
    alter table db1.gz add primary key(gz_id); 
    保证每个员工只能发1遍工资  且有员工编号的员工才能发工资
    mysql> insert into db1.gz values (1,53000);  报错
    mysql> insert into db1.gz values (9,58000);  报错
    mysql> insert into db1.gz values (NULL,80000); 报错

3 案例3：MySQL索引

3.1 问题

完成如下练习：

练习索引的创建、查看、删除、添加
验证索引

3.2 方案

使用规则：

一个表中可以有多个index
任何数据类型的表头都可以设置索引
表头值可以重复，也可以赋NULL值
通常在where条件中的表头上设置Index
index索引标志MUL

3.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：练习索引的创建、查看、删除、添加

1)建表时创建索引命令格式

    CREATE TABLE  库.表(
    字段列表 ,
    INDEX(字段名) ,
    INDEX(字段名) 
    );

例子

    Create database  home;
    Use home;
    CREATE TABLE tea4(
    id char(6),
    name varchar(6),
    age int(3),
    gender ENUM('boy','girl') DEFAULT 'boy',
    INDEX(id),INDEX(name)
    );

查看索引

    查看表头是否有索引    
    des  库.表；

例子

    mysql> desc home.tea4;
    +--------+--------------------+------+-----+---------+-------+
    | Field  | Type               | Null | Key | Default | Extra |
    +--------+--------------------+------+-----+---------+-------+
    | id     | char(6)            | YES   | MUL | NULL    |       |
    | name   | varchar(6)         | YES  | MUL | NULL    |       |
    | age    | int(3)              | YES |     | NULL    |       |
    | gender | enum('boy','girl') | YES  |     | boy     |       |
    +--------+--------------------+------+-----+---------+-------+
    4 rows in set (0.00 sec)
    mysql> system ls /var/lib/mysql/home/tea4.ibd  保存排队信息的文件
    /var/lib/mysql/home/tea4.ibd
    mysql>

查看索引详细信息

    show index   from   库.表；

例子

    show  index   from  home.tea4 \G
    *************************** 1. row ***************************
            Table: tea4     #表名
       Non_unique: 1
         Key_name: id   #索引名   （默认索引名和表头名相同，删除索引时，使用的索引名）
     Seq_in_index: 1
      Column_name: id   #表头名
        Collation: A
      Cardinality: 0
         Sub_part: NULL
           Packed: NULL
             Null: 
       Index_type: BTREE      #索引类型
          Comment: 
    Index_comment: 
    *************************** 2. row ***************************
            Table: tea4   #表名
       Non_unique: 1
         Key_name: name  #索引名
     Seq_in_index: 1
      Column_name: name  #表头名
        Collation: A
      Cardinality: 0
         Sub_part: NULL
           Packed: NULL
             Null: 
       Index_type: BTREE  #排队算法
          Comment: 
    Index_comment: 
    2 rows in set (0.00 sec)
    mysql>

删除索引

    命令格式   DROP  INDEX   索引名   ON  库.表；

例子

    mysql> drop index id on home.tea4 ;
    mysql> desc  home.tea4;
    +--------+--------------------+------+-----+---------+-------+
    | Field  | Type               | Null | Key | Default | Extra |
    +--------+--------------------+------+-----+---------+-------+
    | id     | char(6)            | YES   |     | NULL    |       |
    | name   | varchar(6)         | YES  | MUL | NULL    |       |
    | age    | int(3)             | YES |     | NULL    |       |
    | gender | enum('boy','girl') | YES  |     | boy     |       |
    +--------+--------------------+------+-----+---------+-------+
    4 rows in set (0.14 sec)
    mysql> show  index   from  home.tea4 \G
    *************************** 1. row ***************************
            Table: tea4
       Non_unique: 1
         Key_name: name
     Seq_in_index: 1
      Column_name: name
        Collation: A
      Cardinality: 0
         Sub_part: NULL
           Packed: NULL
             Null: 
       Index_type: BTREE
          Comment: 
    Index_comment: 
    1 row in set (0.00 sec)
    mysql>

已有表添加索引命令

    CREATE  INDEX  索引名  ON  库.表(字段名)；

例子

    mysql> create  index nianling on home.tea4(age);
    mysql> desc home.tea4;
    +--------+--------------------+------+-----+---------+-------+
    | Field  | Type               | Null | Key | Default | Extra |
    +--------+--------------------+------+-----+---------+-------+
    | id     | char(6)            | YES   |     | NULL    |       |
    | name   | varchar(6)         | YES  | MUL | NULL    |       |
    | age    | int(3)             | YES | MUL | NULL    |       |
    | gender | enum('boy','girl') | YES  |     | boy     |       |
    +--------+--------------------+------+-----+---------+-------+
    4 rows in set (0.00 sec)
    mysql> show  index   from  home.tea4 \G
    *************************** 1. row ***************************
            Table: tea4
       Non_unique: 1
         Key_name: name
     Seq_in_index: 1
      Column_name: name
        Collation: A
      Cardinality: 0
         Sub_part: NULL
           Packed: NULL
             Null: 
       Index_type: BTREE
          Comment: 
    Index_comment: 
    *************************** 2. row ***************************
            Table: tea4
       Non_unique: 1
         Key_name: nianling   设置的索引名
     Seq_in_index: 1
      Column_name: age  表头名
        Collation: A
      Cardinality: 0
         Sub_part: NULL
           Packed: NULL
             Null: 
       Index_type: BTREE
          Comment: 
    Index_comment: 
    2 rows in set (0.00 sec)
    mysql>

步骤二：验证索引

    mysql> desc tarena.user;
    +----------+-------------+------+-----+---------+----------------+
    | Field    | Type        | Null | Key | Default | Extra          |
    +----------+-------------+------+-----+---------+----------------+
    | id       | int         | NO   | PRI | NULL    | auto_increment |
    | name     | char(20)    | YES  |     | NULL    |                |
    | password | char(1)     | YES  |     | NULL    |                |
    | uid      | int         | YES  |     | NULL    |                |
    | gid      | int         | YES  |     | NULL    |                |
    | comment  | varchar(50) | YES  |     | NULL    |                |
    | homedir  | varchar(80) | YES  |     | NULL    |                |
    | shell    | char(30)    | YES  |     | NULL    |                |
    +----------+-------------+------+-----+---------+----------------+
    8 rows in set (0.00 sec)

2）使用name表头做筛选条件,查找记录

    mysql> select * from tarena.user where name="sshd";
    +----+------+----------+------+------+-------------------------+-----------------+---------------+
    | id | name | password | uid  | gid  | comment                 | homedir         | shell         |
    +----+------+----------+------+------+-------------------------+-----------------+---------------+
    | 17 | sshd | x        |   74 |   74 | Privilege-separated SSH | /var/empty/sshd | /sbin/nologin |
    +----+------+----------+------+------+-------------------------+-----------------+---------------+
    1 row in set (0.00 sec)

3）验证是否使用索引

    mysql> explain select * from tarena.user where name="sshd" \G
    *************************** 1. row ***************************
               id: 1
      select_type: SIMPLE
            table: user  表名
       partitions: NULL
             type: ALL
    possible_keys: NULL
              key: NULL      使用的索引名
          key_len: NULL
              ref: NULL
             rows: 27         查找的总行数
         filtered: 10.00
            Extra: Using where   额外说明
    1 row in set, 1 warning (0.00 sec)

4）查看表的总行数，查找sshd 用做的是全表扫描

    mysql> select count(*) from tarena.user;
    +----------+
    | count(*) |
    +----------+
    |       28 |
    +----------+
    1 row in set (0.01 sec)

5）给name表头设置索引

    mysql> create index  name on tarena.user(name);
    Query OK, 0 rows affected (0.43 sec)
    Records: 0  Duplicates: 0  Warnings: 0
    mysql> desc tarena.user; 查看
    +----------+-------------+------+-----+---------+----------------+
    | Field    | Type        | Null | Key | Default | Extra          |
    +----------+-------------+------+-----+---------+----------------+
    | id       | int         | NO   | PRI | NULL    | auto_increment |
    | name     | char(20)    | YES  | MUL | NULL    |                |
    | password | char(1)     | YES  |     | NULL    |                |
    | uid      | int         | YES  |     | NULL    |                |
    | gid      | int         | YES  |     | NULL    |                |
    | comment  | varchar(50) | YES  |     | NULL    |                |
    | homedir  | varchar(80) | YES  |     | NULL    |                |
    | shell    | char(30)    | YES  |     | NULL    |                |
    +----------+-------------+------+-----+---------+----------------+
    8 rows in set (0.00 sec)

6）验证索引

    mysql> explain select  * from tarena.user where name="sshd" \G
    *************************** 1. row ***************************
               id: 1
      select_type: SIMPLE
            table: user    表名
       partitions: NULL
             type: ref
    possible_keys: name
              key: name  使用的索引名
          key_len: 21
              ref: const
             rows: 1     查找的总行数
         filtered: 100.00
            Extra: NULL  额外说明
    1 row in set, 1 warning (0.00 sec)

4 案例4：用户管理

4.1 问题

允许所有主机使用root连接数据库服务，对所有库和所有表有完全权限、密码为123qqq…A
允许192.168.88.0/24网段主机使用plj连接数据库服务，仅对gamedb库有完全权限、密码为tarena
允许在本机使用pljadmin用户连接数据库服务器，仅对tarena库有查询、插入、更新、删除记录的权限，密码为NSD2023…a
允许192.168.88.51主机使用yaya用户连接数据库服务，仅对tarena库有查询权限，密码为tarena1
给yaya用户追加，插入记录的权限
撤销plj用户删库、删表、删记录的权限
删除pljadmin用户

4.2 方案

授权是在数据库服务器里添加用户并设置权限及密码；重复执行grant命令时如果库名和用户名不变时，是追加权限。授权步骤如下：

授权信息保存在mysql库的如下表里：

user表保存已有的授权用户及用户对所有库的权限
db表保存已有授权用户对某一个库的访问权限
tables_priv表记录已有授权用户对某一张表的访问权限
columns_priv表记录已有授权用户对某一个表头的访问权限

在192.168.88.50 数据库服务器练习用户授权

在192.168.88.51 数据库服务器测试

4.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：在192.168.88.50 数据库服务器做如下授权练习

命令操作如下所示：

    //数据库管理员登陆
    ]# mysql -uroot -pNSD2023...a

1）允许所有主机使用root连接数据库服务，对所有库和所有表有完全权限、密码为123qqq…A

    mysql> create user root@"%" identified by "123qqq...A"; 创建用户
    Query OK, 0 rows affected (0.08 sec)
    mysql> grant all on *.* to root@"%" ; 授予权限
    Query OK, 0 rows affected (0.13 sec)

2）允许192.168.88.0/24网段主机使用plj连接数据库服务，仅对gamedb库有完全权限、密码为tarena

    mysql> create user plj@"192.168.88.0/24" identified by "tarena"; 创建用户
    Query OK, 0 rows affected (0.06 sec)
    mysql> grant all on  gamedb.*  to plj@"192.168.88.0/24"; 授予权限
    Query OK, 0 rows affected (0.05 sec)

3）允许在本机使用pljadmin用户连接数据库服务器，仅对tarena库有查询、插入、更新、删除记录的权限，密码为NSD2023…a

    mysql> create user pljadmin@"localhost" identified by "NSD2023...a"; 创建用户
    Query OK, 0 rows affected (0.05 sec)
    mysql> grant  select , insert , update,delete on tarena.* to pljadmin@"localhost";授予权限
    Query OK, 0 rows affected (0.06 sec)

4）允许192.168.88.51主机使用yaya用户连接数据库服务，仅对tarena库有查询权限，密码为tarena1

    mysql> create user yaya@"192.168.88.51"  identified by "tarena1" ; 创建用户
    Query OK, 0 rows affected (0.10 sec)
    mysql> grant select on tarena.* to yaya@"192.168.88.51"; 授予权限
    Query OK, 0 rows affected (0.07 sec)

5）给yaya用户追加，插入记录的权限

    mysql> grant insert on tarena.* to yaya@"192.168.88.51";
    Query OK, 0 rows affected (0.05 sec)

6）查看添加的用户

    //添加的用户保存在 mysql库的user表里
    mysql> select  host,user from  mysql.user; 
    +-----------------+------------------+
    | host            | user             |
    +-----------------+------------------+
    | %               | root             |
    | 192.168.88.0/24 | plj              |
    | 192.168.88.51   | yaya             |
    | localhost       | mysql.infoschema |
    | localhost       | mysql.session    |
    | localhost       | mysql.sys        |
    | localhost       | pljadmin         |
    | localhost       | root             |
    +-----------------+------------------+
    8 rows in set (0.00 sec)
    //查看已有用户的访问权限
    mysql> show grants for yaya@"192.168.88.51"; 
    +--------------------------------------------------------------+
    | Grants for yaya@192.168.88.51                                |
    +--------------------------------------------------------------+
    | GRANT USAGE ON *.* TO `yaya`@`192.168.88.51`                   |
    | GRANT SELECT, INSERT ON `tarena`.* TO `yaya`@`192.168.88.51` |
    +--------------------------------------------------------------+
    2 rows in set (0.00 sec)
    //用户对某一个库的访问权限保存在mysql库的db表里
    mysql> select  * from  mysql.db where db="tarena"  and user="yaya" \G
    *************************** 1. row ***************************
                     Host: 192.168.88.51
                       Db: tarena
                     User: yaya
              Select_priv: Y
              Insert_priv: Y
              Update_priv: N
              Delete_priv: N
              Create_priv: N
                Drop_priv: N
               Grant_priv: N
          References_priv: N
               Index_priv: N
               Alter_priv: N
    Create_tmp_table_priv: N
         Lock_tables_priv: N
         Create_view_priv: N
           Show_view_priv: N
      Create_routine_priv: N
       Alter_routine_priv: N
             Execute_priv: N
               Event_priv: N
             Trigger_priv: N
    1 row in set (0.00 sec)
    mysql>

7）撤销plj用户删库、删表、删记录的权限

    mysql> revoke delete,drop on gamedb.* from plj@"192.168.88.0/24" ;

8）修改yaya用户的登陆密码为123456

    mysql> set password for yaya@"192.168.88.51"="123456" ;
    Query OK, 0 rows affected (0.05 sec)

9）删除pljadmin用户

    mysql> drop user pljadmin@"localhost" ;
    Query OK, 0 rows affected (0.04 sec)

步骤二：在192.168.88.51测试授权

命令格式 mysql -h数据库服务器ip地址 –u用户名 -p密码

1）在mysql51连接mysql50 （使用50 添加的yaya 用户）文章来源地址https://www.toymoban.com/news/detail-793443.html

    [root@mysql51 ~]# mysql -h192.168.88.50 -uyaya -p123456
    mysql> show grants; //查看权限
    +--------------------------------------------------------------+
    | Grants for yaya@192.168.88.51                                |
    +--------------------------------------------------------------+
    | GRANT USAGE ON *.* TO `yaya`@`192.168.88.51`                 |
    | GRANT SELECT, INSERT ON `tarena`.* TO `yaya`@`192.168.88.51` |
    +--------------------------------------------------------------+
    2 rows in set (0.00 sec)
    mysql> select user();//查看登陆信息
    +--------------------+
    | user()             |
    +--------------------+
    | yaya@192.168.88.51 |
    +--------------------+
    1 row in set (0.00 sec)
    mysql> insert into  tarena.user(name,uid) values("jim",11); //权限内可以执行
    Query OK, 1 row affected (0.06 sec)
    mysql> delete from  tarena.salary ;
    ERROR 1142 (42000): DELETE command denied to user 'yaya'@'192.168.88.51' for table 'salary'  //超出权限 报错
    mysql>

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