Data access layer: Difference between revisions

Revision as of 17:18, 17 January 2009

Revision as of 21:14, 29 January 2009

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Also, business logic methods from an application can be mapped to the Data Access Layer. So, for example, instead of making a query into a database to fetch all users from several tables the application can call a single method from a DAL which abstracts those database calls.

Applications using a data access layer can be either database- server dependent orindependent. database-independent—ifif the data access layer supports multiple databasesdatabase types, the application becomes able to use whatever databases the DAL can talk to. In either circumstance, having a data access layer provides a centralized ___location for all calls into the database, and thus makes it easier to port the application to other database systems (assuming that 100% of the database interaction is done in the DAL for a given application).

[[Object-Relational Mapping]] tools provide data layers in this fashion, following the [[Active record pattern|active record]] model. The ORM/active-record model is popular with web frameworks, but it has not been proven to be better than a straightforward approach of implementing a collection of ___domain-specific data access functions.