bitsCN.com
1、Mysql errono 1005 : 主外键不是完全一致 , 请检查如下几点:
a、字段是否存在
b、类型是否一致(注意unsigned , powerdesign 生成问题)
c、数据库引擎是否一致
d、字符编码是否一致
e、windows平台下注意修改lower_case_table_names = 0, windows本身不区分文件大小写,改为0之后就区分了可能造成找不到引用的表
2、Mysql errono 121: 外键约束名称重复
3、记录 Mysql WorkBench 中单词缩写意义:
PK: primary key (column is part of a pk)
NN: not null (column is nullable)
UQ: unique (column is part of a unique key)
AI: auto increment (the column is auto incremented when rows are inserted)
BIN: binary (if dt is a blob or similar, this indicates that is binary data, rather than text)
UN: unsigned (for integer types, see docs: “10.2. Numeric Types”)
ZF: zero fill (rather a display related flag, see docs: “10.2. Numeric Types”)
4、mysql 权限设置
//添加远程主机访问MYSQL root权限
insert into user(host,user,password) values('%','root',PASSWORD('root'));
//root 权限授权
grant all privileges on *.* to 'root'@'%' identified by 'root' with grant option;
//更新权限设置
flush privileges;
5、防火墙设置
//打开端口
/sbin/iptables -I INPUT -p tcp --dport 3306 -j ACCEPT
//保存
/etc/rc.d/init.d/iptables save
//查看状态
/etc/init.d/iptables status
6、开机自动运行(实现类似Windows服务)
/sbin/chkconfig --level 2345 mysqld on
/sbin/chkconfig --list
结果如下:
mysqld 0:off 1:off 2:on 3:on 4:on 5:on 6:offbitsCN.com

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL is suitable for small and large enterprises. 1) Small businesses can use MySQL for basic data management, such as storing customer information. 2) Large enterprises can use MySQL to process massive data and complex business logic to optimize query performance and transaction processing.

InnoDB effectively prevents phantom reading through Next-KeyLocking mechanism. 1) Next-KeyLocking combines row lock and gap lock to lock records and their gaps to prevent new records from being inserted. 2) In practical applications, by optimizing query and adjusting isolation levels, lock competition can be reduced and concurrency performance can be improved.

MySQL is not a programming language, but its query language SQL has the characteristics of a programming language: 1. SQL supports conditional judgment, loops and variable operations; 2. Through stored procedures, triggers and functions, users can perform complex logical operations in the database.

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.


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