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ODB is an object-relational mapping (ORM) system for the C++ language. It allows an application developer to persist C++ objects to a relational database without having to deal with tables, columns, or SQL and without manually writing any mapping code. ODB supports C++98/03 and C++11 language standards and comes with optional profiles for Boost and Qt which allow an application developer to seamlessly use value types (data-time, string, binary, uuid, etc.), containers, and smart pointers from these libraries in persistent C++ classes. ODB is free software and is dual-licensed under the GPL and a proprietary license. One notable difference between ODB and other ORM implementations for C++ is its automatic generation of the database mapping code and, optionally, the database schema from the C++ headers that declare the classes. This task is performed by the ODB compiler. The ODB compiler is a real C++ compiler except that instead of producing assembly or machine code, it generates portable C++ which can in turn be compiled by any C++ compiler. The ODB compiler uses the GCC compiler front-end for C++ parsing and is implemented using the new GCC plugin architecture.〔GCC. (GCC Plugins ), 2010-10-01. Retrieved on 2010-10-01.〕 The ODB compiler also provides comprehensive support for database schema evolution, including fully automatic schema migration, support for immediate and gradual data migration, as well as support for soft model changes. The latter feature allows one to work with multiple schema versions using the same C++ classes. The other components of the ODB system include the common runtime library ( libodb) and the database-specific runtime libraries (for example, libodb-mysql). The common runtime library defines object-oriented database interfaces that are used by the application developer to perform various database operations on persistent objects. The database-specific runtimes implement these interfaces for concrete database systems and provide support functionality for the generated database mapping code.To achieve high performance, low overhead, and reliability ODB does not use common database APIs, such as ODBC, to access the relational database. Rather, each database-specific runtime library uses low-level, native C APIs that are specific to each database. ODB currently supports the MySQL, SQLite, PostgreSQL, Oracle, and SQL Server databases. Bulk/batch operations are supported for Oracle and SQL Server. The application can also use multiple databases (for example, MySQL, SQLite, etc.) at the same time. Multi-database support comes in the ''static'' and ''dynamic'' flavors with the latter allowing the application to dynamically load the database support code for individual database if and when necessary. ODB is not a framework. There is no common base type that all persistent classes should derive from nor are there any restrictions on the data member types in persistent classes. Existing classes can be made persistent with a few or no modifications. ODB is also flexible in the level of insulation it provides to the application developer. It can either completely hide the relational nature of the underlying database or expose some of the details as required. ==Mapping== The mapping of C++ classes to database tables is accomplished through a set of custom #pragma directives that are placed in the C++ header file. They allow the application developer to control various aspects of the mapping such as table and column names, C++ types to SQL types mapping, etc. The following example illustrates a typical persistent class declaration:#pragma db object table("people") class person ; The ODB-specific pragmas can also be placed outside of the class declaration. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ODB (C++)」の詳細全文を読む スポンサード リンク
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