Data access layer: Difference between revisions

Revision as of 02:58, 11 March 2012

Revision as of 07:49, 25 August 2012

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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]].

ForFu example,DAL the DAL might return a reference to an [[object (computer science)|object]] (in terms of [[object-oriented programming]]) complete with its attributes instead of a [[row]] of [[Field (computer science)|fields]] from a database [[table (database)|table]]. This allows the client (or user) modules to be created with a higher level of [[abstraction]]. This kind of model could be implemented by creating a class of data access methods that directly reference a corresponding set of database stored procedures. Another implementation could potentially retrieve or write records to or from a file system. The DAL hides this complexity of the underlying data store from the external world.

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.