Data access layer: Difference between revisions

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Latest revision as of 05:13, 24 April 2024

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{{Short description|Layer of a computer program}}

A '''data access layer''' ('''DAL''') in computer software is a [[layer (object-oriented design)|layer]] of a [[computer program]] which provides simplified access to [[data]] stored in [[persistent storage]] of some kind, such as an [[entity relationship|entity-relational]] [[database]]. This [[acronym]] is prevalently used in [[Microsoft]] environments.

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For example, instead of using commands such as ''insert'', ''delete'', and ''update'' to access a specific table in a database, a class and a few stored procedures could be created in the database. The procedures would be called from a method inside the class, which would return an object containing the requested values. Or, the insert, delete and update commands could be executed within simple functions like ''registeruser'' or ''loginuser'' stored within the data access layer.

Also, business logic methods from an application can be mapped to the Datadata Accessaccess Layerlayer. 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 or independent. If the data access layer supports multiple database 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).