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）
[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>