The relational adapters provide sophisticated data retrieval facilities as well as transaction processing and application development tools for updating and maintaining tables resident on the Relational Database Management System (RDBMS). The FOCUS transaction processors Maintain and MODIFY support interactive maintenance procedures as well as batch maintenance using external input files.

The adapters can manage multi-table, multi-record processing supported by all the constructs of a complete programming language (for example, PERFORM groups, computations, data value validations, error handling, GOTO commands, and IF-THEN-ELSE logic). They permit you to update multiple tables in a single procedure. They respect all RDBMS referential integrity rules while, optionally, maintaining their own referential integrity restrictions that you can specify within the update procedures themselves or in the Master Files.

Additionally, you can embed SQL statements (the language required by the RDBMS) directly into FOCUS application code to take advantage of SQL commands that control updates and locks (COMMIT WORK, ROLLBACK WORK), create RDBMS objects (CREATE INDEX, CREATE TABLE), and define security privileges (GRANT, REVOKE). With the Direct SQL Passthru facility, you can even include SQL SELECT statements in report requests and retrieve answer sets from the RDBMS. A Dialogue Manager variable indicates the success or failure of each SQL command. You can create new tables with SQL commands or with the FOCUS CREATE FILE command.

FOCUS complements RDBMS security features by permitting controlled data access at the user, table, field, or field-value levels. You can use FOCUS security to enhance existing RDBMS security.

The adapters translate FOCUS retrieval and update requests into an equivalent set of SQL statements. They also initiate and monitor communication between themselves and the RDBMS, and provide descriptive error message and recovery support when necessary.

The two distinct components of the adapters are Read and Write:

• The Read component translates FOCUS retrieval requests (such as TABLE and GRAPH) into SQL statements that define the request to the RDBMS. When the RDBMS returns an answer set in response to these statements, the adapter passes the answer set to the FOCUS report writer. The report writer can process data from any FOCUS-readable file.
• The Write component generates SQL statements from standard Maintain or MODIFY requests that retrieve and maintain data stored in RDBMS tables.