MySQL 5.5.21

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

Download MySQL Latest Version Why is this app published on FileHorse? (More info)

# Functionality Added or Changed
* A new CMake option, MYSQL_PROJECT_NAME, can be set on Windows or Mac OS X to be used in the project name.
# Bugs Fixed
* Performance: InnoDB Storage Engine: Memory allocation for InnoDB tables was reorganized to reduce the memory overhead for large numbers of tables or partitions, avoiding situations where the “resident set size” could grow regardless of FLUSH TABLES statements. The problem was most evident for tables with large row size. Some of the memory that was formerly allocated for every open table is now allocated only when the table is modified for the first time.
* Incompatible Change: An earlier change (in MySQL 5.1.62 and 5.5.21) was found to modify date-handling behavior in General Availability-status series (MySQL 5.1 and 5.5). This change has been reverted. The change was that several functions became more strict when passed a DATE() function value as their argument, thus they rejected incomplete dates with a day part of zero. These functions were affected: CONVERT_TZ(), DATE_ADD(), DATE_SUB(), DAYOFYEAR(), LAST_DAY(), TIMESTAMPDIFF(), TO_DAYS(), TO_SECONDS(), WEEK(), WEEKDAY(), WEEKOFYEAR(), YEARWEEK(). The previous behavior has been restored.
* InnoDB Storage Engine: A Valgrind error was fixed in the function os_aio_init().
* InnoDB Storage Engine: The server could crash when creating an InnoDB temporary table under Linux, if the $TMPDIR setting points to a tmpfs filesystem and innodb_use_native_aio is enabled, as it is by default in MySQL 5.5.4 and higher. The entry in the error log looked like: 101123 2:10:59 InnoDB: Operating system error number 22 in a file operation. InnoDB: Error number 22 means 'Invalid argument'. The crash occurred because asynchronous I/O is not supported on tmpfs in some Linux kernel versions. The workaround was to turn off the innodb_use_native_aio setting or use a different temporary directory. The fix causes InnoDB to turn off the innodb_use_native_aio setting automatically if it detects that the temporary file directory does not support asynchronous I/O.
* InnoDB Storage Engine: References to C preprocessor symbols and macros HAVE_purify, UNIV_INIT_MEM_TO_ZERO, and UNIV_SET_MEM_TO_ZERO were removed from the InnoDB source code. They were only used in debug builds instrumented for Valgrind. They are replaced by calls to the UNIV_MEM_INVALID() macro.
* InnoDB Storage Engine: The MySQL server could halt with an assertion error: InnoDB: Failing assertion: page_get_n_recs(page) > 1 Subsequent restarts could fail with the same error. The error occurred during a purge operation involving the InnoDB change buffer. The workaround was to set the configuration option innodb_change_buffering=inserts.
* InnoDB Storage Engine: With 1024 concurrent InnoDB transactions running concurrently and the innodb_file_per_table setting enabled, a CREATE TABLE operation for an InnoDB table could fail. The .ibd file from the failed CREATE TABLE was left behind, preventing the table from being created later, after the load had dropped. The fix adds error handling to delete the erroneous .ibd file. This error was less likely to occur in MySQL 5.5 and 5.6, because raising the number of InnoDB undo slots increased the number of simultaneous transactions needed to trigger the bug, from 1K to 128K.
* Replication: Executing mysqlbinlog with the --start-position=N option, where N was equal either to 0 or to a value greater than the length of the dump file, caused it to crash. This issue was introduced in MySQL 5.5.18 by the fix for Bug #32228 and Bug #11747416.
* Replication: On Windows replication slave hosts, STOP SLAVE took an excessive length of time to complete when the master was down.
* A query that used an index on a CHAR column referenced in a BETWEEN clause could return invalid results.
* Expressions that compared a BIGINT column with any non-integer constant were performed using integers rather than decimal or float values, with the result that the constant could be truncated. This could lead to any such comparison that used <, >, <=, >=, =, !=/<>, IN, or BETWEEN yielding false positive or negative results.
* When the optimizer performed conversion of DECIMAL values while evaluating range conditions, it could produce incorrect results.
* When running mysqldump with both the --single-transaction and --flush-logs options, the flushing of the log performed an implicit COMMIT (see Section 12.3.3, “Statements That Cause an Implicit Commit”), causing more than one transaction to be used and thus breaking consistency.
* It was possible in the event of successive failures for mysqld_safe to restart quickly enough to consume excessive amounts of CPU. Now, on systems that support the sleep and date system utilities, mysqld_safe checks to see whether it has restarted more than 5 times in the current second, and if so, waits 1 second before attempting another restart.
* When used with the --xml option, mysqldump --routines failed to dump any stored routines, triggers, or events.
* It was possible on replication slaves where FEDERATED tables were in use to get timeouts on long-running operations, such as Error 1160 Got an error writing communication packets. The FEDERATED tables did not need to be replicated for the issue to occur.
* If an attempt to initiate a statement failed, the issue could not be reported to the client because it was not prepared to receive any error messages prior to the execution of any statement. Since the user could not execute any queries, they were simply disconnected without providing a clear error. After the fix for this issue, the client is prepared for an error as soon as it attempts to initiate a statement, so that the error can be reported prior to disconnecting the user.
* Using myisamchk with the sort recover method to repair a table having fixed-width row format could cause the row pointer size to be reduced, effectively resulting in a smaller maximum data file size.
* On Windows, the server incorrectly constructed the full path name of the plugin binary for INSTALL PLUGIN and CREATE FUNCTION ... SONAME.
* The stored routine cache was subject to a small memory leak that over time or with many routines being used could result in out-of-memory errors.