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MySQL数据库索引管理————（增删改查）

Wesley13

2021-10-11

1363 0 0
  • 索引的概念
  • 数据库建立索引的原则
  • 查看索引
    • 语法格式
    • 示例
    • 显示信息蚕食描述
  • 普通索引
    • 概述
    • 创建普通索引
      • 创建方式
      • 示例
  • 删除索引
    • 删除索引的方式
    • 示例
  • 唯一索引
    • 概述
    • 创建唯一索引
      • 语法格式
      • 示例
  • 主键索引
    • 概述
    • 创建主键索引
  • 全文索引
    • 概述
    • 创建全文索引
      • 创建方法
      • 示例
  • 组合索引
    • 概述
    • 创建组合索引
      • 创建方式

索引的概念

  • 是一个排序的列表，存储着索引值和这个值所对应的物理地址
  • 无须对整个表进行扫描，通过物理地址就可以找到所需数据
  • 是表中一列或者若干列值排序的方法
  • 需要额外的磁盘空间

数据库建立索引的原则

  1. 确定针对该表的操作是大量的查询操作还是大量的增删改操作;
  2. 尝试建立索引来帮助特定的查询。检查自己的sql语句，为那些频繁在where子句中出现的字段建立索引;
  3. 尝试建立复合索引来进一步提高系统性能。修改复合索引将消耗更长时间，同时复合索引也占磁盘空间;
  4. 对于小型的表，建立索引可能会影响性能;
  5. 应该避免对具有较少值的字段进行索引;
  6. 避免选择大型数据类型的列作为索引。

查看索引

语法格式

1SHOW INDEX FROM 表名;
2SHOW KEYS FROM表名 ;

示例

1mysql> create table grade(
2    -> 学号 int(16) not null,
3    -> 姓名 char(16) not null,
4    -> 班级 char(16) not null,
5    -> 成绩 int(3) not null,
6    -> primary key(学号));
7Query OK, 0 rows affected (0.01 sec)
8mysql> show keys from grade;   //第一种查看方式
9+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
10| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
11+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
12| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
13+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
141 row in set (0.01 sec)
15
16mysql> show index from grade;   //第二种查看方式
17+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
18| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
19+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
20| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
21+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
221 row in set (0.00 sec)
23mysql> show index from grade \G;   //末尾加上\G表示竖向查看
24*************************** 1. row ***************************
25        Table: grade
26   Non_unique: 0
27     Key_name: PRIMARY
28 Seq_in_index: 1
29  Column_name: 学号
30    Collation: A
31  Cardinality: 0
32     Sub_part: NULL
33       Packed: NULL
34         Null: 
35   Index_type: BTREE
36      Comment: 
37Index_comment: 
381 row in set (0.00 sec)
39

显示信息蚕食描述

参数

描述

Table

表的名称

Non_unique

索引值得唯一性，0表示唯一，1表示不唯一

Key_name

索引的名称

Seq_in_index

索引的序列号，从1开始

Column_name

列的名称

普通索引

概述

  • 最基本的索引类型，没有唯─性之类的限制
  • 创建普通索引的方式

创建普通索引

创建方式

1 1. 创建表时创建索引
2 2. CREATE INDEX 索引名 ON 表名 (列名);
3 3. ALTER TABLE 表名 ADD INDEX 索引名 (列名);

示例

1mysql> create table ltp(
2    ->  id int(4) not null primary key auto_increment,
3    ->  name varchar(10) not null,
4    ->  score decimal not null,
5    -> hobby int(2) not null default '1',
6    -> index index_scrore (score));
7Query OK, 0 rows affected (0.01 sec)
8
9mysql> show keys from ltp;
10+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
11| Table | Non_unique | Key_name     | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
12+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
13| tp   |          0 | PRIMARY      |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
14| tp   |          1 | index_scrore |            1 | score       | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
15+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
16mysql> create index name on grade(姓名);  //使用create方式新增索引
17Query OK, 0 rows affected (0.01 sec)
18Records: 0  Duplicates: 0  Warnings: 0
19
20mysql> show keys from grade;  
21+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
22| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
23+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
24| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
25| grade |          1 | name     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
26+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
272 rows in set (0.00 sec)
28mysql> alter table grade add index 姓名(姓名);  //使用alter方式新建索引
29Query OK, 0 rows affected, 1 warning (0.00 sec)
30Records: 0  Duplicates: 0  Warnings: 1
31
32mysql> show keys from grade;   //查看到新增了一条姓名索引
33+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
34| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
35+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
36| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
37| grade |          1 | name     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
38| grade |          1 | 姓名     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
39+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
403 rows in set (0.00 sec)
41

删除索引

删除索引的方式

1DROP INDEX 索引名 ON 表名;
2ALTERTABLE 表名 DROP INDEX 索引名;

示例

1mysql> drop index name on grade;  //删除name索引
2Query OK, 0 rows affected (0.00 sec)
3Records: 0  Duplicates: 0  Warnings: 0
4
5mysql> show index from grade;  //查看，name索引已经被删除
6+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
7| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
8+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
9| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
10| grade |          1 | 姓名     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
11+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
122 rows in set (0.00 sec)
13
14mysql> alter table grade drop index 姓名;  //删除姓名索引
15Query OK, 0 rows affected (0.00 sec)
16Records: 0  Duplicates: 0  Warnings: 0
17
18mysql> show keys from grade;  //查看，删除成功
19+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
20| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
21+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
22| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
23+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
241 row in set (0.00 sec)
25

唯一索引

概述

  • “普通索引”基本相同
  • 与普通索引的区别是索引列的所有值只能出现一次，即必须唯一
  • 创建唯一索引的方式

创建唯一索引

语法格式

11.创建表时创建索引
22.CREATE UNIQUE INDEX 索引名 ON 表名(列名);
33.ALTER TABLE 表名 ADD UNIQUE 索引名(列名);

示例

1mysql> create table lllx (   //创建表的方式创建
2    -> id int(4) not null primary key auto_increment,
3    -> name varchar(10) not null,
4    -> score decimal not null,
5    -> hobby int(2) not null default '1',
6    -> unique index index_scrore (score));
7Query OK, 0 rows affected (0.01 sec)
8
9mysql> show keys from lllx;
10+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
11| Table | Non_unique | Key_name     | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
12+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
13| lllx  |          0 | PRIMARY      |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
14| lllx  |          0 | index_scrore |            1 | score       | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
15+-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
162 rows in set (0.00 sec)
17
18mysql> create unique index name on grade(姓名);   //新建name索引
19Query OK, 0 rows affected (0.00 sec)
20Records: 0  Duplicates: 0  Warnings: 0
21
22mysql> show keys from grade;   //查看索引，新建成功
23+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
24| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
25+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
26| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
27| grade |          0 | name     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
28+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
292 rows in set (0.00 sec)
30 
31mysql> alter table grade drop index name;    //删除name索引
32Query OK, 0 rows affected (0.00 sec)
33Records: 0  Duplicates: 0  Warnings: 0
34
35
36mysql> alter table grade add unique 姓名(姓名);  //新建姓名索引
37Query OK, 0 rows affected (0.00 sec)
38Records: 0  Duplicates: 0  Warnings: 0
39
40mysql> show index from grade;  //查看，新建成功
41+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
42| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
43+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
44| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
45| grade |          0 | 姓名     |            1 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
46+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
472 rows in set (0.00 sec)
48
49mysql> alter table grade drop index 姓名;   //删除姓名索引
50Query OK, 0 rows affected (0.00 sec)
51Records: 0  Duplicates: 0  Warnings: 0
52

主键索引

概述

  • 是一种特殊的唯一索引，指定为“PRIMARY KEY"，
  • 一个表只能有一个主键，不允许有空值
  • 创建表时必须创建，创建后不能删除

创建主键索引

1mysql> create table test(   //创建表的方式创建索引
2    -> id int(10) not null auto_increment,
3    -> title char(255) not null,
4    -> primary key (`id`));
5Query OK, 0 rows affected (0.01 sec)
6
7mysql> show keys from test;
8+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
9| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
10+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
11| test  |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
12+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
131 row in set (0.00 sec)
14

全文索引

概述

  • MySQL从3.23.23版开始支持全文索引和全文检索
  • 索引类型为FULLTEXT
  • 可以在CHAR、VARCHAR或者TEXT类型的列上创建

创建全文索引

创建方法

1在创建表时创建索引
2CREATE FULLTEXT INDEX 索引名 ON 表名(列名);
3ALTER TABLE 表名 ADD FULLTEXT 索引名(列名);

示例

1mysql> create table article (  新建方式创建索引
2    -> 标题 char(48) not null,
3    -> 目录 varchar(255) default null,
4    -> 正文 varchar(8096) not null,
5    -> primary key (标题),
6    -> fulltext (正文));
7Query OK, 0 rows affected (0.34 sec)
8
9mysql> show keys from article;
10+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
11| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
12+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
13| article |          0 | PRIMARY  |            1 | 标题        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
14| article |          1 | 正文     |            1 | 正文        | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
15+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
162 rows in set (0.00 sec)
17
18mysql> alter table article add fulltext page(目录);  //alter方式新创建page索引
19Query OK, 0 rows affected (0.02 sec)
20Records: 0  Duplicates: 0  Warnings: 0
21
22mysql> show keys from article;  //查看，创建成功
23+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
24| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
25+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
26| article |          0 | PRIMARY  |            1 | 标题        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
27| article |          1 | 正文     |            1 | 正文        | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
28| article |          1 | page     |            1 | 目录        | NULL      |           0 |     NULL | NULL   | YES  | FULLTEXT   |         |               |
29+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
303 rows in set (0.00 sec)
31
32mysql> drop index page on article;  //删除page索引
33Query OK, 0 rows affected (0.02 sec)
34Records: 0  Duplicates: 0  Warnings: 0
35
36mysql> create fulltext index mulu on article(目录);  //使用create方式创建mulu索引
37Query OK, 0 rows affected (0.02 sec)
38Records: 0  Duplicates: 0  Warnings: 0
39
40mysql> show index from article;  查看，创建成功
41+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
42| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
43+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
44| article |          0 | PRIMARY  |            1 | 标题        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
45| article |          1 | 正文     |            1 | 正文        | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
46| article |          1 | mulu     |            1 | 目录        | NULL      |           0 |     NULL | NULL   | YES  | FULLTEXT   |         |               |
47+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
483 rows in set (0.00 sec)
49
50

组合索引

概述

  • 可以是单列上创建的索引，也可以是在多列上创建的索引
  • 最左原则，从左往右依次执行
  • 创建组合索引的方式

创建组合索引

创建方式

11.创建表时创建索引
22.CREATE UNIQUE INDEX 索引名 ON 表名(列名1，列名2，……);
33.ALTER TABLE 表名 ADD UNIQUE 索引名(列名1，列名2，……);
4
5
6mysql> create table users (    //创建表的方式创建
7    -> name char(9),
8    -> age int(3),
9    -> sex tinyint(1),
10    -> index user (name,age,sex));
11Query OK, 0 rows affected (0.00 sec)
12mysql> show keys from user;
13+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
14| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
15+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
16| user  |          1 | user     |            1 | name        | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               |
17| user  |          1 | user     |            2 | age         | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               |
18| user  |          1 | user     |            3 | sex         | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               |
19+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
203 rows in set (0.01 sec)
21
22mysql> create unique index student on grade(学号,姓名,成绩);  //给学号,姓名,成绩这几列创建索引，名为student
23Query OK, 0 rows affected (0.01 sec)
24Records: 0  Duplicates: 0  Warnings: 0
25
26mysql> show index from grade;   //查看，创建成功
27+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
28| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
29+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
30| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
31| grade |          0 | student  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
32| grade |          0 | student  |            2 | 姓名        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
33| grade |          0 | student  |            3 | 成绩        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
34+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
354 rows in set (0.00 sec)
36
37mysql> drop index student on grade;  //删除student索引
38Query OK, 0 rows affected (0.01 sec)
39Records: 0  Duplicates: 0  Warnings: 0
40
41mysql> alter table grade add fulltext 学生(姓名,班级); //给姓名,班级两列创建全文索引，索引名为学生
42Query OK, 0 rows affected, 1 warning (0.05 sec)
43Records: 0  Duplicates: 0  Warnings: 1
44
45mysql> show keys from grade;  查看，创建成功
46+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
47| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
48+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
49| grade |          0 | PRIMARY  |            1 | 学号        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
50| grade |          1 | 学生     |            1 | 姓名        | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
51| grade |          1 | 学生     |            2 | 班级        | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
52+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
533 rows in set (0.00 sec)
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