[mysql]数据库复习
2016-05-19 11:25
507 查看
1.创建，插入，查看，备份，恢复
重开一个命令行窗口备份：mysqldump是命令行指令！
显示出现了一个问题，但已成功备份出sql文件，上网查可能是mysql版本问题或操作系统设置问题，待解决：
备份出的文件：
恢复：只能恢复数据，所以要先创建库：
恢复库的另一种办法：同样是windows命令：
2.表相关
3.乱码问题：显式通知mysql码表-------->通知以gb2312编码存入，但库、表其实还是创建时的码表，要正确显示又要设置按gb2312显示，并且重开窗口还是原来的样子，想一劳永逸，一开始创建时就要指定码表！
可以更改my.ini配置文件中mysql客-户-端码表（注意不要改mysql服务端码表！--->默认utf8），但一般不这么做！！！
注意的安全问题：更新或删除时，一定注意先把后边的where条件写好，再在前面添加数据，不然忘了写where条件，结果是致命的！！！
实际中一般要经常备份！！！
更新或删除时还要注意表关联的问题！
4.（待复习，更新）表查询（复杂的多表查询，子查询）
5.外键约束
6.表设计：（数据库三范式）
一对多的复杂对象数据存入表：先各自独立建表，再在多的一方设置另一方为外键约束，描述数据关系。
多对多的对象关系：设计一个中间表描述关系，中间表的相应字段分别加两方表为外键约束。
一对一：主从关系（如人和身份证），外键约束加唯一约束、非空约束（主可以没有从，从不能没有主），因为从的主键有唯一、非空约束，所以把主键设置外键约束即可
自关联：（家族族谱）增加字段parent_id，并设置外键约束为自身的id字段----------->应用：设计一棵无限级分类的树(以后要用二叉树方案)
例子：
多对多
设计：
一对一
设计：
自关联：一个列的值来自另一列
设计：自连接的表
注：此前那个person表被idcard表设置成外键约束，所以无法删除，只能先删除idcard表，怎样删除外键待查。
无限级分类示意：
不按三范式的设计：放在一张表里，会出现冗余，但查询性能较好，因为不用查多表。要求查询性能高的方案可能会这样设计。
Microsoft Windows XP [版本 5.1.2600] (C) 版权所有 1985-2001 Microsoft Corp. C:\Documents and Settings\Administrator>mysql -uroot -p Enter password: **** Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 to server version: 5.0.22-community-nt Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | test | +--------------------+ 3 rows in set (0.08 sec) mysql> create database mydb2 charset utf8; Query OK, 1 row affected (0.06 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb2 | | mysql | | test | +--------------------+ 4 rows in set (0.00 sec) mysql> create database mydb3 charset utf8 collate utf8_general_ci; Query OK, 1 row affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb2 | | mydb3 | | mysql | | test | +--------------------+ 5 rows in set (0.00 sec) mysql> show create database mydb3; +----------+----------------------------------------------------------------+ | Database | Create Database | +----------+----------------------------------------------------------------+ | mydb3 | CREATE DATABASE `mydb3` /*!40100 DEFAULT CHARACTER SET utf8 */ | +----------+----------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> drop database mydb2; Query OK, 0 rows affected (0.28 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb3 | | mysql | | test | +--------------------+ 4 rows in set (0.00 sec) mysql> use mydb3; Database changed mysql> create table test( -> id int unsigned auto_increment primary key, -> username char(20) not null, -> password char(20) not null, -> description varchar(50)) engine=InnoDB charset=utf8; Query OK, 0 rows affected (0.34 sec) mysql> insert into test values(null,'Xiao Bai','6395749','Fight For Beijing!'); Query OK, 1 row affected (0.09 sec) mysql> show create table test; +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ | Table | Create Table | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ | test | CREATE TABLE `test` ( `id` int(10) unsigned NOT NULL auto_increment, `username` char(20) NOT NULL, `password` char(20) NOT NULL, `description` varchar(50) default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ 1 row in set (0.05 sec) mysql> select * from test; +----+----------+----------+--------------------+ | id | username | password | description | +----+----------+----------+--------------------+ | 1 | Xiao Bai | 6395749 | Fight For Beijing! | +----+----------+----------+--------------------+ 1 row in set (0.01 sec)
重开一个命令行窗口备份：mysqldump是命令行指令！
Microsoft Windows XP [版本 5.1.2600] (C) 版权所有 1985-2001 Microsoft Corp. C:\Documents and Settings\Administrator>mysqldump -uroot -p mydb3>c:\XiaoBai.sql Enter password: **** mysqldump: mysqldump: Couldn't execute 'SHOW TRIGGERS LIKE 'test'': Can't create /write to file 'C:\WINDOWS\TEMP\#sql_9c_0.MYI' (Errcode: 13) (1)
显示出现了一个问题，但已成功备份出sql文件，上网查可能是mysql版本问题或操作系统设置问题，待解决：
备份出的文件：
-- MySQL dump 10.10 -- -- Host: localhost Database: mydb3 -- ------------------------------------------------------ -- Server version 5.0.22-community-nt /*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */; /*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */; /*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */; /*!40101 SET NAMES utf8 */; /*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */; /*!40103 SET TIME_ZONE='+00:00' */; /*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */; /*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */; /*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */; /*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */; -- -- Table structure for table `test` -- DROP TABLE IF EXISTS `test`; CREATE TABLE `test` ( `id` int(10) unsigned NOT NULL auto_increment, `username` char(20) NOT NULL, `password` char(20) NOT NULL, `description` varchar(50) default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- -- Dumping data for table `test` -- /*!40000 ALTER TABLE `test` DISABLE KEYS */; LOCK TABLES `test` WRITE; INSERT INTO `test` VALUES (1,'Xiao Bai','6395749','Fight For Beijing!'); UNLOCK TABLES; /*!40000 ALTER TABLE `test` ENABLE KEYS */;
恢复：只能恢复数据，所以要先创建库：
mysql> drop database mydb3; Query OK, 1 row affected (0.11 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | test | +--------------------+ 3 rows in set (0.02 sec) mysql> create database mydb3; Query OK, 1 row affected (0.00 sec) mysql> use mydb3; Database changed mysql> source c:\XiaoBai.sql Query OK, 0 rows affected (0.03 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.11 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 1 row affected (0.01 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb3 | | mysql | | test | +--------------------+ 4 rows in set (0.00 sec) mysql> show create table test; +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ | Table | Create Table | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ | test | CREATE TABLE `test` ( `id` int(10) unsigned NOT NULL auto_increment, `username` char(20) NOT NULL, `password` char(20) NOT NULL, `description` varchar(50) default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------+ 1 row in set (0.00 sec) mysql> select * from test; +----+----------+----------+--------------------+ | id | username | password | description | +----+----------+----------+--------------------+ | 1 | Xiao Bai | 6395749 | Fight For Beijing! | +----+----------+----------+--------------------+ 1 row in set (0.00 sec) mysql>
恢复库的另一种办法：同样是windows命令：
mysql -uroot -proot mydb3<c:\XiaoBai.sql
2.表相关
Microsoft Windows XP [版本 5.1.2600] (C) 版权所有 1985-2001 Microsoft Corp. C:\Documents and Settings\Administrator>mysql -uroot -p Enter password: **** Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 to server version: 5.0.22-community-nt Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb3 | | mysql | | test | +--------------------+ 4 rows in set (0.11 sec) mysql> use mydb3; Database changed mysql> show tables; +-----------------+ | Tables_in_mydb3 | +-----------------+ | test | +-----------------+ 1 row in set (0.01 sec) mysql> desc test; +-------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | username | char(20) | NO | | NULL | | | password | char(20) | NO | | NULL | | | description | varchar(50) | YES | | NULL | | +-------------+------------------+------+-----+---------+----------------+ 4 rows in set (0.23 sec) mysql> describe test; +-------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | username | char(20) | NO | | NULL | | | password | char(20) | NO | | NULL | | | description | varchar(50) | YES | | NULL | | +-------------+------------------+------+-----+---------+----------------+ 4 rows in set (0.01 sec) mysql> show columns from test; +-------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | username | char(20) | NO | | NULL | | | password | char(20) | NO | | NULL | | | description | varchar(50) | YES | | NULL | | +-------------+------------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec) mysql> alter table test add gender char(1) after password; Query OK, 1 row affected (0.28 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> alter table test add image blob; Query OK, 1 row affected (0.14 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> desc test; +-------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | username | char(20) | NO | | NULL | | | password | char(20) | NO | | NULL | | | gender | char(1) | YES | | NULL | | | description | varchar(50) | YES | | NULL | | | image | blob | YES | | NULL | | +-------------+------------------+------+-----+---------+----------------+ 6 rows in set (0.02 sec) mysql> alter table test modify password varchar(30); Query OK, 1 row affected (0.13 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> alter table test modify username varchar(30); Query OK, 1 row affected (0.14 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> alter table test drop gender; Query OK, 1 row affected (0.14 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> desc test; +-------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | username | varchar(30) | YES | | NULL | | | password | varchar(30) | YES | | NULL | | | description | varchar(50) | YES | | NULL | | | image | blob | YES | | NULL | | +-------------+------------------+------+-----+---------+----------------+ 5 rows in set (0.00 sec) mysql> rename table test to user; Query OK, 0 rows affected (0.03 sec) mysql> show tables; +-----------------+ | Tables_in_mydb3 | +-----------------+ | user | +-----------------+ 1 row in set (0.00 sec) mysql>
mysql> alter table user character set utf8; Query OK, 1 row affected (0.16 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> alter table user charset utf8; Query OK, 1 row affected (0.14 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> show create table user; +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------------------------------------+ | Table | Create Table | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------------------------------------+ | user | CREATE TABLE `user` ( `id` int(10) unsigned NOT NULL auto_increment, `username` varchar(30) default NULL, `password` varchar(30) default NULL, `description` varchar(50) default NULL, `image` blob, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | +-------+----------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ------------------------------------+ 1 row in set (0.00 sec)
mysql> alter table user change column username username varchar(60); Query OK, 1 row affected (0.14 sec) Records: 1 Duplicates: 0 Warnings: 0 mysql> \s -------------- mysql Ver 14.12 Distrib 5.0.22, for Win32 (ia32) Connection id: 1 Current database: mydb3 Current user: root@localhost SSL: Not in use Using delimiter: ; Server version: 5.0.22-community-nt Protocol version: 10 Connection: localhost via TCP/IP Server characterset: utf8 Db characterset: utf8 Client characterset: utf8 Conn. characterset: utf8 TCP port: 3306 Uptime: 1 hour 16 min 10 sec Threads: 1 Questions: 24 Slow queries: 0 Opens: 25 Flush tables: 1 Open tab les: 0 Queries per second avg: 0.005 --------------
3.乱码问题：显式通知mysql码表-------->通知以gb2312编码存入，但库、表其实还是创建时的码表，要正确显示又要设置按gb2312显示，并且重开窗口还是原来的样子，想一劳永逸，一开始创建时就要指定码表！
mysql> show variables like 'chara%';
+--------------------------+----------------------------------------------------
-----+
| Variable_name | Value
|
+--------------------------+----------------------------------------------------
-----+
| character_set_client | utf8
|
| character_set_connection | utf8
|
| character_set_database | utf8
|
| character_set_filesystem | binary
|
| character_set_results | utf8
|
| character_set_server | utf8
|
| character_set_system | utf8
|
| character_sets_dir | F:\Program Files\MySQL\MySQL Server 5.0\share\chars
ets\ |
+--------------------------+----------------------------------------------------
-----+
8 rows in set (0.03 sec)
mysql> set character_set_client=gb2312;
Query OK, 0 rows affected (0.08 sec)
mysql> show variables like 'chara%';
+--------------------------+----------------------------------------------------
-----+
| Variable_name | Value
|
+--------------------------+----------------------------------------------------
-----+
| character_set_client | gb2312
|
| character_set_connection | utf8
|
| character_set_database | utf8
|
| character_set_filesystem | binary
|
| character_set_results | utf8
|
| character_set_server | utf8
|
| character_set_system | utf8
|
| character_sets_dir | F:\Program Files\MySQL\MySQL Server 5.0\share\chars
ets\ |
+--------------------------+----------------------------------------------------
-----+
8 rows in set (0.00 sec)
mysql> insert into user(id,username) values('2','小白');
Query OK, 1 row affected (0.06 sec)
mysql> select * from user;
+----+----------+----------+--------------------+-------+
| id | username | password | description | image |
+----+----------+----------+--------------------+-------+
| 1 | Xiao Bai | 6395749 | Fight For Beijing! | NULL |
| 2 | 灏忕櫧 | NULL | NULL | NULL |
+----+----------+----------+--------------------+-------+
2 rows in set (0.00 sec)
mysql> set charset gb2312;
Query OK, 0 rows affected (0.02 sec)
mysql> select * from user;
+----+----------+----------+--------------------+-------+
| id | username | password | description | image |
+----+----------+----------+--------------------+-------+
| 1 | Xiao Bai | 6395749 | Fight For Beijing! | NULL |
| 2 | 小白 | NULL | NULL | NULL |
+----+----------+----------+--------------------+-------+
2 rows in set (0.02 sec)
mysql>mysql> show variables like 'chara%'; +--------------------------+---------------------------------------------------- -----+ | Variable_name | Value | +--------------------------+---------------------------------------------------- -----+ | character_set_client | gb2312 | | character_set_connection | utf8 | | character_set_database | utf8 | | character_set_filesystem | binary | | character_set_results | gb2312 | | character_set_server | utf8 | | character_set_system | utf8 | | character_sets_dir | F:\Program Files\MySQL\MySQL Server 5.0\share\chars ets\ | +--------------------------+---------------------------------------------------- -----+ 8 rows in set (0.00 sec) mysql> set character_set_results=gb2312; Query OK, 0 rows affected (0.00 sec) mysql> select * from user; +----+----------+----------+--------------------+-------+ | id | username | password | description | image | +----+----------+----------+--------------------+-------+ | 1 | Xiao Bai | 6395749 | Fight For Beijing! | NULL | | 2 | 小白 | NULL | NULL | NULL | +----+----------+----------+--------------------+-------+ 2 rows in set (0.00 sec)
可以更改my.ini配置文件中mysql客-户-端码表（注意不要改mysql服务端码表！--->默认utf8），但一般不这么做！！！
注意的安全问题：更新或删除时，一定注意先把后边的where条件写好，再在前面添加数据，不然忘了写where条件，结果是致命的！！！
实际中一般要经常备份！！！
更新或删除时还要注意表关联的问题！
4.（待复习，更新）表查询（复杂的多表查询，子查询）
5.外键约束
mysql> create table husband -> (id int primary key, -> name varchar(40) -> ); Query OK, 0 rows affected (0.09 sec) mysql> create table wife -> (id int primary key, -> name varchar(40), -> husband_id int, -> constraint husband_id_FK foreign key(husband_id) references husband(id) -> ); Query OK, 0 rows affected (0.08 sec)
mysql> insert into husband(id,name) values(1,'张三'); ERROR 1406 (22001): Data too long for column 'name' at row 1 mysql> set charset gb2312; Query OK, 0 rows affected (0.06 sec)
mysql> insert into husband(id,name) values(1,'张三'); ERROR 1062 (23000): Duplicate entry '1' for key 1 mysql> insert into husband(id,name) values(2,'李四'); Query OK, 1 row affected (0.02 sec) mysql> insert into wife(id,name,husband_id) values(1,'陈琪',5); ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint f ails (`mydb3/wife`, CONSTRAINT `husband_id_FK` FOREIGN KEY (`husband_id`) REFERE NCES `husband` (`id`)) mysql> insert into wife(id,name,husband_id) values(1,'陈琪',2); Query OK, 1 row affected (0.03 sec) mysql> select * from husband; +----+------+ | id | name | +----+------+ | 1 | 张三 | | 2 | 李四 | +----+------+ 2 rows in set (0.05 sec) mysql> select * from wife; +----+------+------------+ | id | name | husband_id | +----+------+------------+ | 1 | 陈琪 | 2 | +----+------+------------+ 1 row in set (0.02 sec)
6.表设计：（数据库三范式）
一对多的复杂对象数据存入表：先各自独立建表，再在多的一方设置另一方为外键约束，描述数据关系。
多对多的对象关系：设计一个中间表描述关系，中间表的相应字段分别加两方表为外键约束。
一对一：主从关系（如人和身份证），外键约束加唯一约束、非空约束（主可以没有从，从不能没有主），因为从的主键有唯一、非空约束，所以把主键设置外键约束即可
自关联：（家族族谱）增加字段parent_id，并设置外键约束为自身的id字段----------->应用：设计一棵无限级分类的树(以后要用二叉树方案)
例子：
多对多
设计：
mysql> create table teacher -> ( -> id int primary key, -> name varchar(40), -> salary decimal(8,2) -> ); Query OK, 0 rows affected (0.16 sec) mysql> create table student -> (id int primary key, -> name varchar(40)); Query OK, 0 rows affected (0.11 sec) mysql> create table teacher_student -> ( -> teacher_id int, -> student_id int, -> primary key(teacher_id,student_id), -> constraint teacher_id_FK foreign key(teacher_id) references teacher(id), -> constraint student_id_FK foreign key(student_id) references student(id) -> ); Query OK, 0 rows affected (0.14 sec)
一对一
设计：
mysql> create table person -> ( -> id int primary key, -> name varchar(40) -> ); Query OK, 0 rows affected (0.20 sec) mysql> create table idcard -> ( -> id int primary key, -> city varchar(40), -> constraint id_FK foreign key(id) references person(id)); Query OK, 0 rows affected (0.11 sec)
自关联：一个列的值来自另一列
设计：自连接的表
mysql> drop table person; ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constrai nt fails mysql> drop table idcard; Query OK, 0 rows affected (0.03 sec) mysql> drop table person; Query OK, 0 rows affected (0.05 sec) mysql> create table person -> ( -> id int primary key, -> name varchar(40), -> parent_id int, -> constraint parent_id_FK foreign key(parent_id) references person(id)); Query OK, 0 rows affected (0.08 sec)
注：此前那个person表被idcard表设置成外键约束，所以无法删除，只能先删除idcard表，怎样删除外键待查。
无限级分类示意：
不按三范式的设计：放在一张表里，会出现冗余，但查询性能较好，因为不用查多表。要求查询性能高的方案可能会这样设计。
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