MySQL管理表和索引

Posted 2020-08-12

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创建数据库：

mysql> HELP CREATE DATABASE; 查看创建数据库的帮助信息

CREATE DATABASE|SCHEMA [IF NOT EXISTS]（在数据库不存在的时候才创建） db_name [CHARACTER SET=](指定字符集) [COLLATE=]（指定排序规则）

mysql> show character set; 显示所有的字符集

mysql> show collation; 查看排序规则

mysql> CREATE SCHEMA IF NOT EXISTS students CHARACTER SET ‘gbk‘ COLLATE ‘gbk_chinese_ci‘;

[[email protected] ~]# ls /mydata/data/students

db.opt

[[email protected] ~]# cat /mydata/data/students/db.opt

default-character-set=gbk

default-collation=gbk_chinese_ci

修改数据库：

mysql> help alter database;

ALTER {DATABASE | SCHEMA} [db_name]

alter_specification ...

ALTER {DATABASE | SCHEMA} db_name

UPGRADE DATA DIRECTORY NAME

alter_specification:

[DEFAULT] CHARACTER SET [=] charset_name

| [DEFAULT] COLLATE [=] collation_name

删除数据库：

mysql> help drop database;

DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

创建表：

mysql> help create table;

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name 直接定义一张空表

(create_definition,...)

[table_options]

[partition_options]

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name 或者从其他表中查询出数据，并以之创建新表

[(create_definition,...)]

[table_options]

[partition_options]

select_statement

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name 仿造其他表创建一个空表

{ LIKE old_tbl_name | (LIKE old_tbl_name) }

table_option:

ENGINE [=] engine_name 指定表的存储引擎

| AUTO_INCREMENT [=] value 自动增长从哪个值开始

| AVG_ROW_LENGTH [=] value 平均长度

| [DEFAULT] CHARACTER SET [=] charset_name 字符集

| CHECKSUM [=] {0 | 1} 是否启用校验和

| [DEFAULT] COLLATE [=] collation_name 排序规则

| COMMENT [=] ‘string‘ 注释

| CONNECTION [=] ‘connect_string‘

| DATA DIRECTORY [=] ‘absolute path to directory‘数据目录

| DELAY_KEY_WRITE [=] {0 | 1}

| INDEX DIRECTORY [=] ‘absolute path to directory‘索引目录

| INSERT_METHOD [=] { NO | FIRST | LAST }

| KEY_BLOCK_SIZE [=] value

| MAX_ROWS [=] value 最多允许存储多少行

| MIN_ROWS [=] value

| PACK_KEYS [=] {0 | 1 | DEFAULT}

| PASSWORD [=] ‘string‘

| ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT} 行格式

| TABLESPACE tablespace_name [STORAGE {DISK|MEMORY|DEFAULT}] 表空间

| UNION [=] (tbl_name[,tbl_name]...)

create tables [if not exists] tb_name (cool_name col_defination,constraint)

create table tb1 (ID int unsigned not null auto_increment primary key,NAME char(20) not null,AGE tinyint not null);

create table tb2 (ID int unsigned not null auto_increment ,NAME char(20) not null,AGE tinyint not null,primary key(ID),unique key(NAME),index(AGE));

mysql> create table courses(CID tinyint unsigned not null auto_increment primary key, COUSE varchar(50) not null);

mysql> show table status like ‘courses‘\G 查看表的存储引擎

*************************** 1. row ***************************

Name: courses

Engine: InnoDB

Version: 10

Row_format: Compact

Rows: 0

Avg_row_length: 0

Data_length: 16384

Max_data_length: 0

Index_length: 0

Data_free: 0

Auto_increment: 1

Create_time: 2016-10-01 19:48:43

Update_time: NULL

Check_time: NULL

Collation: gbk_chinese_ci

Checksum: NULL

Create_options:

Comment:

1 row in set (0.00 sec)

mysql> drop table courses;指定存储引擎

mysql> create table courses(CID tinyint unsigned not null auto_increment primary key, COUSE varchar(50) not null) engine=myisam;

mysql> show table status like ‘courses‘\G

*************************** 1. row ***************************

Name: courses

Engine: MyISAM

Version: 10

Row_format: Dynamic

Rows: 0

Avg_row_length: 0

Data_length: 0

Max_data_length: 281474976710655

Index_length: 1024

Data_free: 0

Auto_increment: 1

Create_time: 2016-10-01 19:53:36

Update_time: 2016-10-01 19:53:36

Check_time: NULL

Collation: gbk_chinese_ci

Checksum: NULL

Create_options:

Comment:

1 row in set (0.00 sec)

往表里插入数据

mysql> insert into courses (COUSE) values (‘yuwen‘),(‘shuxue‘),(‘wuli‘);

mysql> select * from courses; 查看

+-----+--------+

| CID | COUSE |

+-----+--------+

| 1 | yuwen |

| 2 | shuxue |

| 3 | wuli |

| 4 | yuwen |

| 5 | shuxue |

| 6 | wuli |

+-----+--------+

6 rows in set (0.00 sec)

mysql> show indexes from courses; 查看表上的索引

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| courses | 0 | PRIMARY | 1 | CID | A | 6 | NULL | NULL | | BTREE | | |

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

1 row in set (0.00 sec)

mysql> create table courses2 select * from courses where CID <=2; 以courses中的数据来创建一个新表

mysql> select * from courses2;

+-----+--------+

| CID | COUSE |

+-----+--------+

| 1 | yuwen |

| 2 | shuxue |

+-----+--------+

2 rows in set (0.00 sec)

mysql> desc courses2; 查看表结构

+-------+---------------------+------+-----+---------+-------+

+-------+---------------------+------+-----+---------+-------+

| CID | tinyint(3) unsigned | NO | | 0 | |

+-------+---------------------+------+-----+---------+-------+

2 rows in set (0.01 sec)

mysql> desc courses;

+-------+---------------------+------+-----+---------+----------------+

+-------+---------------------+------+-----+---------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

+-------+---------------------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

mysql> create table test like courses;以现有的表结构创建一个空表

mysql> desc test;

+-------+---------------------+------+-----+---------+----------------+

+-------+---------------------+------+-----+---------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

+-------+---------------------+------+-----+---------+----------------+

单字段

primary key

unique key

单或多字段

pramary key (col,...)

unique key (col,...)

index (col,...)

修改表：

mysql> help alter table;

ALTER [ONLINE | OFFLINE] [IGNORE] TABLE tbl_name

[alter_specification [, alter_specification] ...]

[partition_options]

mysql> desc test;

+-------+---------------------+------+-----+---------+----------------+

+-------+---------------------+------+-----+---------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

+-------+---------------------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

mysql> show indexes from test;

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| test | 0 | PRIMARY | 1 | CID | A | 0 | NULL | NULL | | BTREE | | |

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

1 row in set (0.00 sec)

往test表添加一个唯一键索引

mysql> alter table test add unique key (COUSE);

mysql> show indexes from test;

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| test | 0 | PRIMARY | 1 | CID | A | 0 | NULL | NULL | | BTREE | | |

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

修改一个字段的名称：

mysql> alter table test change COUSE COURSE varchar(50) not null;

mysql> desc test;

+--------+---------------------+------+-----+---------+----------------+

+--------+---------------------+------+-----+---------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

+--------+---------------------+------+-----+---------+----------------+

新增一个字段：

mysql> alter table test add STARTTIME date default ‘2016-10-02‘;

mysql> desc test;

+-----------+---------------------+------+-----+------------+----------------+

+-----------+---------------------+------+-----+------------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

| STARTTIME | date | YES | | 2016-10-02 | |

+-----------+---------------------+------+-----+------------+----------------+

给表重命名：

mysql> alter table test rename to COURSES10;

mysql> show tables ;

+--------------------+

| Tables_in_students |

+--------------------+

| COURSES10 |

| courses |

| courses2 |

+--------------------+

或者:

mysql> rename table COURSES10 to test;

mysql> show tables ;

+--------------------+

| Tables_in_students |

+--------------------+

| courses |

| courses2 |

| test |

+--------------------+

删除表：

mysql> help drop table;

DROP [TEMPORARY] TABLE [IF EXISTS]

tbl_name [, tbl_name] ...

[RESTRICT | CASCADE]

mysql> create table student (SID int unsigned not null auto_increment primary key,NAME varchar(30),CID int not null);

mysql> insert into student (NAME,CID) value (‘zhangsan‘,‘1‘),(‘lisi‘,‘2‘),(‘wangwu‘,‘3‘);

mysql> select * from student;

+-----+----------+-----+

| SID | NAME | CID |

+-----+----------+-----+

| 1 | zhangsan | 1 |

| 2 | lisi | 2 |

| 3 | wangwu | 3 |

+-----+----------+-----+

mysql> select * from courses;

+-----+--------+

| CID | COUSE |

+-----+--------+

| 1 | yuwen |

| 2 | shuxue |

| 3 | wuli |

| 4 | yuwen |

| 5 | shuxue |

| 6 | wuli |

+-----+--------+

使用组合查询：

mysql> select NAME,COUSE from student,courses where student.CID=courses.CID;

+----------+--------+

| NAME | COUSE |

+----------+--------+

| zhangsan | yuwen |

| lisi | shuxue |

| wangwu | wuli |

+----------+--------+

删除表的字段：

mysql> delete from student where NAME=‘wangwu‘;

修改表引擎：

mysql> alter table courses engine=innodb;

引用型约束：（innodb才支持外键）

mysql> alter table student modify CID tinyint unsigned not null;

mysql> desc student;

+-------+---------------------+------+-----+---------+----------------+

+-------+---------------------+------+-----+---------+----------------+

| SID | int(10) unsigned | NO | PRI | NULL | auto_increment |

| CID | tinyint(3) unsigned | NO | | NULL | |

+-------+---------------------+------+-----+---------+----------------+

mysql> desc courses;

+-------+---------------------+------+-----+---------+----------------+

+-------+---------------------+------+-----+---------+----------------+

| CID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |

+-------+---------------------+------+-----+---------+----------------+

mysql> alter table student add foreign key (CID) references courses(CID); 创建一个外键约束

mysql> show indexes from student;

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| student | 0 | PRIMARY | 1 | SID | A | 2 | NULL | NULL | | BTREE | | |

| student | 1 | CID | 1 | CID | A | 2 | NULL | NULL | | BTREE | | |

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

mysql> select * from courses;

+-----+--------+

| CID | COUSE |

+-----+--------+

| 1 | yuwen |

| 2 | shuxue |

| 3 | wuli |

| 4 | yuwen |

| 5 | shuxue |

| 6 | wuli |

+-----+--------+

mysql> insert into student (NAME,CID) value (‘maliu‘,‘7‘);

ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`students`.`student`, CONSTRAINT `student_ibfk_1` FOREIGN KEY (`CID`) REFERENCES `courses` (`CID`))

mysql> delete from courses where CID=‘3‘;

ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`students`.`student`, CONSTRAINT `student_ibfk_1` FOREIGN KEY (`CID`) REFERENCES `courses` (`CID`))

创建索引：

mysql> show indexes from student;

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| student | 0 | PRIMARY | 1 | SID | A | 3 | NULL | NULL | | BTREE | | |

| student | 1 | CID | 1 | CID | A | 3 | NULL | NULL | | BTREE | | |

+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

mysql> create index NAME_ON_STUDENT on student (NAME) using btree;

mysql> show indexes from student;

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| student | 0 | PRIMARY | 1 | SID | A | 3 | NULL | NULL | | BTREE | | |

| student | 1 | CID | 1 | CID | A | 3 | NULL | NULL | | BTREE | | |

| student | 1 | NAME_ON_STUDENT | 1 | NAME | A | 3 | NULL | NULL | YES | BTREE | | |

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

索引创建：

create index INDEX_NAME on TB_NAME (col,...);

mysql> help create index;

CREATE [ONLINE|OFFLINE] [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name

[index_type]

ON tbl_name (index_col_name,...)

[index_option] ...

index_col_name:

col_name [(length)] [ASC | DESC] #length从最左侧开始进行比较 ASC升序，DESC降序

index_type:

USING {BTREE | HASH}

index_option:

KEY_BLOCK_SIZE [=] value

| index_type

| WITH PARSER parser_name

| COMMENT ‘string‘

删除索引：

mysql> help drop index;

DROP [ONLINE|OFFLINE] INDEX index_name ON tbl_name

mysql> drop index NAME_ON_STUDENT on student;

mysql> create index NAME_ON_STUDENT on student (NAME(5) desc) using btree;

mysql> show indexes from student;

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| student | 0 | PRIMARY | 1 | SID | A | 3 | NULL | NULL | | BTREE | | |

| student | 1 | CID | 1 | CID | A | 3 | NULL | NULL | | BTREE | | |

| student | 1 | NAME_ON_STUDENT | 1 | NAME | A | 3 | 5 | NULL | YES | BTREE | | |

+---------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

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