MySQL 的engine类型


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最开始用MySQL Administrator建数据库的时候,表缺省是InnoDB类型,也就没有在意。后来用Access2MySQL导数据的时候发现只能导成MyISAM类型的表,不知道这两种类型有什么区别,就去查了查。原来是MyISAM类型不支持事务处理等高级处理,而InnoDB类型支持。MyISAM类型的表强调的是性能,其执行数度比InnoDB类型更快,但是不提供事务支持,而InnoDB提供事务支持已经外部键等高级数据库功能。这样就可以根据数据表不同的用处是用不同的存储类型。



Storage Engines and Table Types
MySQL supports several storage engines that act as handlers for different table types. MySQL storage engines include both those that handle transaction-safe tables and those that handle non-transaction-safe tables:

The original storage engine was ISAM, which managed non-transactional tables. This engine has been replaced by MyISAM and should no longer be used. It is deprecated in MySQL 4.1, and is removed in subsequent MySQL release series.

In MySQL 3.23.0, the MyISAM and HEAP storage engines were introduced. MyISAM is an improved replacement for ISAM. The HEAP storage engine provides in-memory tables. The MERGE storage engine was added in MySQL 3.23.25. It allows a collection of identical MyISAM tables to be handled as a single table. All three of these storage engines handle non-transactional tables, and all are included in MySQL by default. Note that the HEAP storage engine has been renamed the MEMORY engine.

The InnoDB and BDB storage engines that handle transaction-safe tables were introduced in later versions of MySQL 3.23. Both are available in source distributions as of MySQL 3.23.34a. BDB is included in MySQL-Max binary distributions on those operating systems that support it. InnoDB also is included in MySQL-Max binary distributions for MySQL 3.23. Beginning with MySQL 4.0, InnoDB is included by default in all MySQL binary distributions. In source distributions, you can enable or disable either engine by configuring MySQL as you like.

The EXAMPLE storage engine was added in MySQL 4.1.3. It is a "stub" engine that does nothing. You can create tables with this engine, but no data can be stored in them or retrieved from them. The purpose of this engine is to serve as an example in the MySQL source code that illustrates how to begin writing new storage engines. As such, it is primarily of interest to developers.

NDB Cluster is the storage engine used by MySQL Cluster to implement tables that are partitioned over many computers. It is available in source code distributions as of MySQL 4.1.2 and binary distributions as of MySQL-Max 4.1.3.

The ARCHIVE storage engine was added in MySQL 4.1.3. It is used for storing large amounts of data without indexes in a very small footprint.

The CSV storage engine was added in MySQL 4.1.4. This engine stores data in text files using comma-separated values format.

The BLACKHOLE storage engine was added in MySQL 4.1.11. This engine accepts but does not store data and retrievals always return an empty set.


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