Using Interoperable SQL
One API-many databases
By Ken North
As more sites post pages with active database content, SQL is becoming a required skill for many Web developers. A plethora of Rapid Application Development (RAD) tools, Web database connectors, database engines, object layers, data-aware components, and other software is available, but in exploring the subtleties and nuances of these tools, developers sometimes fail to investigate the SQL techniques they support; specifically, the ability to work with more than one DBMS.
Hundreds of database products support SQL, in part because database vendors participate in the consortia and organizations that create standards. ANSI and ISO published SQL standards in 1986, 1989, and 1992, and work continues on a future standard known as "SQL3." Standards provide an incubator effect that nurtures product development, and SQL is no exception. SQL is ubiquitous, and database industry experts have even described it as "intergalactic dataspeak." Nonetheless, vendor-specific extensions create differences in SQL dialects.
Developers who limit themselves to a single SQL dialect will have trouble creating scripts, programs, or Web pages capable of operating with more than one SQL platform. The solutions are either a transparent database gateway or a multidatabase application programming interface (API). Gateways are middleware products that provide connections to databases in several dozen formats, allowing vendor-specific SQL to operate on those databases. A gateway provides the type mapping and other logic necessary to unify heterogeneous databases into a single, logical database.
