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Data-Access Layer

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  • Last Updated : 24 Jan, 2023
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In this article, we are going to learn about the Business Logic Layer in Database Management systems. A DBMS usually consists of various layers where each one has a specific kind of task it performs. The main purpose of the layered structure is to implement abstraction in Database systems. Change in one schema must not affect the other schema. This architecture allows the Database Administrator to design the schema and implement methods to allow secured access to the stored data.

The Data-Access Layer (DAL) is a component of a software architecture that is responsible for managing the data storage and retrieval of an application. It sits between the business-logic layer and the data storage system and provides an abstraction layer that allows the business-logic layer to interact with the data storage system without being aware of its specific implementation.

The DAL is responsible for performing tasks such as:
-Connecting to the data storage system and managing the connection.
-Generating and executing SQL queries or other data access commands to retrieve and store data.
-Mapping the data from the data storage system to the application’s data objects and vice versa.
-Handling errors and exceptions related to data access.
-Providing support for transactions and other data access features.

The DAL is designed to be reusable and independent of the business logic and data storage implementation. This allows the application to be easily modified or extended without affecting the underlying data access code.

The DAL can be implemented using different data access technologies, such as ADO.NET, JDBC, or ORM (Object-relational mapping) libraries. The choice of technology will depend on the specific requirements of the application and the data storage system being used.

In summary, The Data-Access Layer (DAL) is a component of a software architecture that is responsible for managing the data storage and retrieval of an application. It sits between the business-logic layer and the data storage system and provides an abstraction layer that allows the business-logic layer to interact with the data storage system without being aware of its specific implementation. The DAL is designed to be reusable and independent of the business logic and data storage implementation. It can be implemented using different data access technologies and it provides support for transactions and other data access features.

Data-Access Layer (DAL) 

Data-Access Layer is a layer in an application that provides easy and simplified access to data stored in persistent storage, such as an entity-relational database or any database for that matter. It is layer that exists between the Business Logic Layer (BLL) and the storage layer

Let us understand some terminologies involved: 

1. Data-Access Object (DAO): They are entities that are collectively known as the Data Access Layer (DAL). A DAL might be a single class, or it might be composed of multiple Data Access Objects (DAOs). 

2. Business Logic Layer: The business logic layer consists of all the objects and functionalities which handle the business logic of the application, this is where the main implementation of an application takes place and it is very unique for each application. 

3. Storage Layer: The actual database where data is stored, upon which CRUD operations can be performed. This might be some remote or cloud storage.

 

Data Access Layer

Data Access Layer

Whenever a specific data query or update is required by the Application (BLL), the request is sent to the Data Access Layer, which then takes appropriate actions to ensure that the requested data or updation is performed, this results in a level of abstraction wherein the Business Layer will only know which function or methods to call, and it does not have to know the actual architecture or details of the entire Database.
 

Purpose/Importance of having a DAL:

  • Provides a centralized location from where calls are made onto the database(s).
  • Provides a layer of abstraction as a developer working on the Business Logic need not worry about the way in which data is stored or their CRUD operations.
  • A Data-Access Layer (DAL) can support multiple databases, so the application is able to make use of any database as per its requirement.
  • Because segregating the data access code, enables better maintainability and easy migration of the database.

Example

Let us assume an airline ticket reservation system, when a user attempts to view the flight availability from the front-end, the business logic layer will send the query request to the Data-Access Layer, from here its this layer’s job to interact with the storage and obtain the queried results. The Business logic layer is not concerned with the way in which data is represented in the storage, whether it is relational or non-relational types. It is the job of the DAL to retrieve the required data from one or more locations from the storage(s) and send it back to the Business Logic Layer, which is converted to user-understandable format, then sent to the front-end.

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