MySQL 5.5.29

MySQL 是一套開源且由社群驅動的關聯式資料庫管理系統，主要用來儲存、管理與檢索數據，並以速度快、可靠性高和易於使用著稱。它最鮮明的特色在於具備高度的可擴展性，能從小型應用一路撐起大型企業系統，同時提供最佳化的查詢執行與索引技術，確保資料處理效率；安全性方面也內建多種驗證與加密機制，並支援複寫與叢集以達成高可用性。目前由 Oracle 持續維護，更新相當活躍，在同類開發者工具中屬於主流首選，使用者評價普遍不錯，累積的評分人數也相當可觀。

這套軟體適合需要建構資料驅動應用程式的開發者，無論是網站後端、企業內部系統或數據分析平台，都能派上用場。它主要透過命令列介面運作，對熟悉指令的進階使用者較友善，但市面上有許多第三方圖形介面工具可補足操作門檻。與同分類的 BlueStacks、Turbo C++ 或 VMware 等工具相比，MySQL 專注於資料庫核心服務，並非整合開發環境或虛擬化方案，取捨上更偏向純粹的資料層需求。授權為開源軟體，提供 Windows 與 macOS 版本，但介面僅支援英文，使用前需留意語系與操作習慣。

MySQL 是一款開源且由 community-driven RDBMS，為儲存、管理與檢索數據提供強大且具可擴展性的平台。

它以速度快、可靠性高且易於使用而聞名，使其成為小型應用程式與大型企業系統的理想選擇。

由 Oracle Corporation 開發，MySQL Community Server 提供了一套完整的工具與功能，讓開發者能夠輕鬆建構動態且由數據驅動的應用程式。

Key Features

Scalability
它能處理海量數據，並可毫不費力地擴展以滿足日益增長的需求。

Performance
憑藉優化的 Query Execution 與 Indexing 技術，它能確保快速的數據檢索與處理速度。

Security
它提供多種 Authentication 機制與 Encryption 選項，以保護敏感數據的安全。

High Availability
它支援 Replication 與 Clustering，可實現冗餘備援並確保數據的持續可用性。

Flexibility
MySQL 相容於多種作業系統並支援多種程式語言，具有極高的通用性。

User Interface

MySQL Database Server 主要透過 Command-line Interface (CLI) 運作，適合經驗豐富的使用者與開發者。

然而，許多第三方工具提供了 Graphical User Interface (GUI)，簡化了資料庫管理任務，例如建立表格、執行查詢以及監控效能。

常見的 GUI 選項包括 phpMyAdmin, MySQL Workbench 以及 Navicat。

Installation and Setup

它為 Windows, macOS 與 Linux 等主流作業系統提供安裝套件。

安裝過程非常簡單，通常只需執行安裝程式並按照提示操作即可。

在設定過程中，使用者可以配置資料庫設定、定義存取權限以及指定儲存選項。

此外，它也可以作為 Web 開發 Stack 的一部分（例如 XAMPP 或 WAMP）進行安裝，以建立完整的開發環境。

How to Use

為了有效地使用 MySQL，使用者應對 SQL (Structured Query Language) 以及資料庫管理原則有基本的了解。

它提供豐富的 SQL 指令集用於建立、檢索、更新與刪除數據。開發者可以使用專用的 Connector 與 Library 將 MySQL 整合至其選擇的程式語言中，例如 Java 的 MySQL Connector/J 或 Python 的 MySQL Connector/Python。

目前有大量的官方文件與線上資源可幫助使用者學習並精通 MySQL 的功能。

FAQ

Q: 我可以將現有的資料庫遷移到 MySQL Community Server 嗎？
A: 可以，它提供了將資料庫從其他 RDBMS（如 Oracle, SQL Server 和 PostgreSQL）遷移的工具與公用程式。

Q: MySQL 適合大型應用程式嗎？
A: 絕對適合！MySQL 的 Scalability 與 Performance 使其成為管理企業級應用程式數據的絕佳選擇。

Q: 免費開源版本的 MySQL 有任何限制嗎？
A: 開源版本提供了豐富的功能，但若需要進階功能（如即時分析與企業級支援），使用者可以考慮訂閱制且功能更強大的 MySQL Enterprise Edition。

Q: 我可以防止未經授權的存取來保護我的 MySQL 資料庫嗎？
A: 可以，它提供了強大的安全功能，包括 User Authentication、Access Control 與 Encryption 機制，以保護您的數據免於未經授權的存取。

Q: MySQL 支援 Stored Procedures 和 Triggers 嗎？
A: 是的，它支援 Stored Procedures, Triggers 以及 Functions，允許開發者在資料庫內執行複雜的操作並自動化任務。

Alternatives

雖然 MySQL Database Server 在 RDBMS 市場佔據主導地位，但仍有其他替代方案可供選擇，且各有其獨特功能與優勢。值得關注的替代產品包括：

Microsoft SQL Server: 針對 Windows 平台設計，提供強大的企業級功能、與 Microsoft 產品的無縫整合以及卓越的 Scalability。

PostgreSQL: 以注重標準合規性與進階功能著稱，是一款適用於複雜數據場景的強大開源 DBMS。

Oracle Database: 作為商業 RDBMS，提供極高性能、進階安全性和廣泛的管理工具，適合大型企業級應用。

SQLite: 理想的小型輕量化應用選擇，是一款 Serverless DBMS，在簡便性、可移植性與零配置部署方面表現出色。

Pricing

MySQL 主要分為兩個版本：Community Edition (免費開源) 與 Enterprise Edition (商業版，提供額外功能與支援)。

Community Edition 是大多數使用者的熱門選擇，而 Enterprise Edition 則需要訂閱，並提供量身打造的企業級進階功能。

此外，他們還提供以下產品：

• MySQL HeatWave
• MySQL Enterprise Edition
• MySQL Standard Edition
• MySQL Classic Edition
• MySQL Cluster CGE
• MySQL Embedded (OEM/ISV)

System Requirements

MySQL 的系統需求依據所使用的作業系統與版本而異。

一般而言，它支援 Windows, macOS 以及各種 Linux 發行版。

根據資料庫的大小與複雜程度，需要充足的磁碟空間、記憶體與處理能力。

PROS

• 開源且免費的 Community Server Edition
• 高效能與高 Scalability
• 強大的安全功能
• 豐富的文件紀錄與活躍的社群支援
• 相容於多種程式語言

CONS

• Command-line Interface 對初學者來說可能較具挑戰性
• 部分進階功能僅限於 Enterprise Edition
• 複雜的設定可能需要額外的配置與優化

Conclusion

MySQL Community Server 是一款可靠且功能豐富的 RDBMS，在管理關聯式資料庫方面享有盛名。其速度、Scalability 與通用性使其適用於從小型專案到企業級系統的各種應用。

雖然 Command-line Interface 對初學者而言可能需要一定的學習曲線，但 GUI 工具的出現簡化了資料庫管理流程。憑藉龐大的社群與詳盡的文件，它將繼續作為軟體開發生態系統中的核心工具。無論您是開發者、數據分析師還是企業主，MySQL 都能讓您高效地組織與存取數據，為您的專案與計畫帶來成功。

Also Available: MySQL for Mac

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# Functionality Added or Changed
* The SHOW AUTHORS and SHOW CONTRIBUTORS statements are now deprecated in MySQL 5.5 and have been removed in MySQL 5.6.
# Bugs Fixed
* Performance: InnoDB: The timing values for low-level InnoDB read operations were adjusted for better performance with fast storage devices, such as SSD. This enhancement primarily affects read operations for BLOB columns in compressed tables.
* Important Change: InnoDB: A DML statement using the index merge access method could lock many rows from the table, even when those rows were not part of the final result set. This fix reduces the excessive locking by releasing the locks of unmatched rows. This optimization affects only transactions with isolation level equal to or less strict than READ COMMITTED; it does not apply to transactions using REPEATABLE READ or SERIALIZABLE isolation level.
* InnoDB: An online DDL operation for an InnoDB table incorrectly reported an empty value ('') instead of the correct key value when it reported a duplicate key error for a unique index using an index prefix.
* InnoDB: If a CREATE TABLE statement failed due to a disk full error, some memory allocated during the operation was not freed properly.
* InnoDB: With the innodb_file_per_table setting enabled, a DROP TABLE operation could cause a crash, due to a race condition that depended on the timing of pending I/O requests.
* InnoDB: If the server crashed at the specific point when a change buffer entry was being merged into a buffer pool page, the transaction log and the change buffer were left in an inconsistent state. After a restart, MySQL could crash after reading the corresponding secondary index page. The problem was more likely to occur in MySQL 5.5 or later, where the original insert buffering mechanism was generalized to cover other operations.
* InnoDB: Inserting data of varying record lengths into an InnoDB table that used compression could cause the server to halt with an error.
* InnoDB: If a table was defined with an index key length very close to the upper length limit of 3072, a query against that table could cause a serious error.
* InnoDB: When an auto-increment column used a FLOAT or DOUBLE data type, if the auto-increment value became very large (larger than the maximum unsigned long long value), subsequent inserts could fail or cause the server to halt.
* InnoDB: If a transaction was started with a consistent snapshot, then new indexes were added to the table while the transaction was in progress, a subsequent UPDATE statement could incorrectly encounter the error:
- HA_ERR_TABLE_DEF_CHANGED: insufficient history for index
- This issue could cause an assertion error in debug builds.
* InnoDB: The error message was improved for the case where an UPDATE failed because the row included several BLOB values greater than 768 bytes each, causing the size of a row to exceed half the page size. The old message, was misleading; it suggested using BLOBs, when the 768-byte prefix for each BLOB column was the cause of the limit error:
- Error Code 1118: Row size too large. The maximum row size for the used table type, not counting BLOBs, is 8126. You have to change some columns to TEXT or BLOBs
- A workaround for the problem was to create the table with the ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED clause, which is now suggested in the message.
* InnoDB: In rare circumstances, MySQL could apply InnoDB undo records out of order during a ROLLBACK of an operation that modified a BLOB column. This issue could cause an assertion error in debug builds:
- !bpage->file_page_was_freed
* Replication: Updates writing user variables whose values were never set on a slave while using --replicate-ignore-table could cause the slave to fail.
* Replication: Backtick (`) characters were not always handled correctly in internally generated SQL statements, which could sometimes lead to errors on the slave.
* Replication: Following an insert into a nontransactional table that failed due to insufficient disk space, the server did not properly clean up all pending events, leading to an assert or possibly to other errors.
* Very long database names in queries could cause the server to exit.
* Within a stored procedure, executing a multiple-table DELETE statement that used a very long table alias could cause the server to exit.
* Very long table aliases in queries could cause the server to exit.
* Attempting to create an auto-increment column in an InnoDB table with a NULL type attribute could cause a serious error.
* A DELETE statement for an InnoDB table could write incorrect transaction metadata into a record, causing the server to halt with an error. To work around this issue, reduce the specified length of the primary key to less than 1K bytes.
* Repeated execution of a query containing a subquery that used MAX() could result in increasing memory consumption.
* USE dbname could fail with Unknown database when dbname contained multiple backtick (`) characters.
* The configure.pl script that converts GNU configure options to CMake equivalents generated erroneous output for the --with-client-ldflags and --with-mysqld-ldflags options. It now ignores those options.
* SHOW PROFILE could be used to cause excessive server memory consumption.
* The thread cache implementation worked in LIFO rather than FIFO fashion and could result in a thread being denied service (although this was a remote possibility).
* Within a stored program, memory allocated to hold condition information was not released until program exit, leading to excessive memory use.
* Improper memory cleanup could cause the server to exit.
* Granting or revoking the PROXY privilege caused the server to exit if the server was started with --skip-name-resolve.
* CREATE USER and DROP USER could fail to flush the privileges, requiring FLUSH PRIVILEGES to be used explicitly.
* Access to INFORMATION_SCHEMA tables through a view could leak memory.
* A memory leak could occur for queries containing a subquery that used GROUP BY on an outer column.
* On Microsoft Windows with CMake 2.6, the build process would not stop if the create_initial_db step failed.
* The test in mysqld_safe for the presence of the --plugin_dir option and assignment of a default value to it were performed before the actual argument parsing took place.
* CHECK TABLE and REPAIR TABLE could crash if a MyISAM table had a corrupt key (.MYI) file. Now the server produces an error.
* Improper memory cleanup could cause the server to exit.
* A memory leak occurred due to failure to clean up after QUICK_INDEX_MERGE_SELECT/Unique.
* The number of connection errors from a given host as counted by the server was periodically reset, with the result that max_connect_errors was never reached and invalid hosts were never blocked from trying to connect.
* During optimization, ZEROFILL values may be converted to string constants. However, CASE expressions did not handle switching data types after the planning stage, leading to CASE finding a null pointer instead of its argument.
* In debug builds, an InnoDB assertion was overly aggressive about prohibiting an open range.
* On Windows, the Perl version of mysql_install_db created system tables in the mysql database that were not populated properly.
* mysqld_safe ignored the value of the UMASK environment variable, leading to behavior different from mysqld with respect to the access mode of created files. Now mysqld_safe (and mysqld_multi) attempt to approximate the same behavior as mysqld.
* LAST_INSERT_ID(expr) did not work for expr values greater than the largest signed BIGINT value.