SQL Data Access Services Overview

The SQL Data Access Services (SQLDAS) framework allows applications written on the CommonPoint application system to insert and retrieve data to and from standard, commercial SQL databases, and insulates the applications from SQL dialects and vendor-specific connectivity layers.

After reading this chapter you should:

Understand the features that SQLDAS provides
Understand the three SQLDAS interfaces
Decide which interface and services your application requires

SQL dialects

Although SQL is often presented as standard, in reality, many SQL dialects exist. These dialects agree more or less on simple retrieval, such as SELECT commands, but differ in other respects, such as table creation, index specification, and outer join operators. While ISO-ANSI efforts to resolve these differences continue, a solution is many years away, and might be unattainable given the need for individual SQL database vendors to distinguish their product offerings.

Vendor-specific connectivity layers

SQLDAS allows CommonPoint application users to choose both connectivity layer and database at logon time, thereafter isolating the application software from particular server dependencies while permitting custom use of specific database and connectivity features. Using SQLDAS, CommonPoint applications can download and upload data to and from arbitrary SQL data stores through arbitrary connectivity layers without concern for implementation details.

SQL dialects
Vendor-specific connectivity layers
SQLDAS interfaces
Understanding record sources
Understanding how to use SQLDAS
SQLDAS usage considerations

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