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Other than two-tier architecture approach there is another approach available that is three-tier architecture, which is used for Web-based applications. It adds an intermediate layer known as the application server (or Web server) between the client and the database server. The client communicates with the application server, which in turn communicates with the database server. The application server stores the business rules (procedures and constraints) used for accessing data from the database server. It checks the client's credentials before forwarding a request to the database server. When a client requests for information, the application server accepts the request, processes it and sends corresponding database commands to the database server. The database server sends the result back to the application server, which is converted into GUI format and presented to the client. Figure below shows the three-tier architecture.

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