一、什麽是 MySQL
MySQL (发音为 "My Ess Que Ell")是 Tcx 公司开发的一个多人使用、多执行绪的 SQL 资料库 Server。MySQL 主要的目标在快速、稳定和容易使用。
MySQL 可在此 http://www.mysql.net/ 取得。
二、MySQL 的安装
本文所使用的 MySQL 版本为 mysql-3.22.27.tar.gz(原始码档),作业环境为 RedHat6.0 +CLE0.8 。
MySQL 预设情况下会安装至 /usr/local 目录下,不过为了日後移除方便,建议将 mysql 独立安装在 /usr/local/mysql 目录。底下为安装 MySQL 的步骤:
取得 mysql-3.22.27.tar.gz 後, 於 /usr/local 目录下解开:
# cd /usr/local
# tar zxvf mysql-3.22.27.tar.gz
# cd mysql-3.22.27
设定 configure 安装选项,选择安装目录 (prefix)以及支援中文 Big5 码(with-charset=big5):
# ./configure --prefix=/usr/local/mysql
#--with-charset=big5
开始编译并安装:
# make
# make install
# scripts/mysql_install_db
最後一个步骤是用来产生 MySQL grant tables(会建立一个 mysql 资料库和一些 tables,用来管理使用 MySQL 的授权资讯,也就是使用者有哪些使用资料库的权限)。
三、启动、停止 MySQL
要启动 MySQL 的方法:(以本文将 MySQL 安装在 /usr/local/mysql 为例)
# /usr/local/mysql/share/mysql.server start
注意在第一次执行前,须将 mysql.server 设成可执行(chmod 744 mysql.server),另外可将这行指令加在 /etc/rc.d/rc.local 档中,让 MySQL 在开机时自动启动。
要停止 MySQL 的方法:
# /usr/local/mysql/bin/mysqladmin shutdown
如果你为 MySQL Administrator root 帐号(非作业系统的 root)设了密码,要停止 MySQL 则必须像下列这样做,MySQL 会询问你 root 的密码後才会执行 shutdown 的工作:
# /usr/local/mysql/bin/mysqladmin -u root -p shutdown

ACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.

MySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.

MySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.

MySQL is an efficient relational database management system suitable for storing and managing data. Its advantages include high-performance queries, flexible transaction processing and rich data types. In practical applications, MySQL is often used in e-commerce platforms, social networks and content management systems, but attention should be paid to performance optimization, data security and scalability.

The relationship between SQL and MySQL is the relationship between standard languages and specific implementations. 1.SQL is a standard language used to manage and operate relational databases, allowing data addition, deletion, modification and query. 2.MySQL is a specific database management system that uses SQL as its operating language and provides efficient data storage and management.

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB


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