Data Access Library for Eiffel contents structure

ODBC conformance levels and grammar

API Conformance Levels. The ODBC API defines a set of core functions that correspond to the functions in the X/Open and SQL Access Group Call Level Interface specification. ODBC also defines two extended sets of functionality, Level 1 and Level 2. As a rule drivers support at least Level 1 API.

SQL Conformance Levels. ODBC defines a core grammar that roughly corresponds to the X/Open and SQL Access Group SQL CAE specification (1992). ODBC also defines a minimum grammar, to meet a basic level of ODBC conformance, and an extended grammar, to provide for common DBMS extensions to SQL. The following list summarizes the grammar included in each conformance level:

Minimum SQL Grammar:

Core SQL Grammar:

Extended SQL Grammar:

The ODBC SQL grammar is not intended to restrict the set of statements that an application can submit for execution. Drivers should support data source-specific extensions to the SQL language, although interoperable applications should not rely on those extensions.

Before an application can use ODBC, it must initialize ODBC and request an environment. To communicate with a data source, the application must request a connection and connect to the data source. The application uses the environment and connection in subsequent ODBC statements to refer to the environment and specific connection.

An application may request multiple connections for one or more data sources. Each connection is considered a separate transaction space. An active connection can have one or more statement processing streams.

A driver maintains a transaction for each active connection. The application can request that each SQL statement be automatically committed on completion; otherwise, the driver waits for an explicit commit or rollback request from the application. When the driver performs a commit or rollback operation, the driver resets all statement requests associated with the connection.The Driver Manager manages the work of allowing an application to switch connections while transactions are in progress on the current connection.


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Last updated: 2005/02/02 11:51:24