Data access in SQL Database is similar to how you access data in SQL Server. It is based on the Tabular Data Stream (TDS) over secure socket layer (SSL). There are many ways to access data in the SQL Database from your application. You can use client libraries such as ADO.Net or ODBC.
In a typical on-premise scenario, the application and the database reside in the same data center. In a typical Cloud scenario, both application and SQL Database reside in the cloud. A variation is when the application is residing in on-premise and the database is in the cloud. Data transfer in all the cases happen based on the TDS protocol. Let us consider the two scenarios in greater detail.
In the first scenario, the application resides on-premise and the database resides in Windows Azure SQL Database. As shown in Fig:-5.6, Application uses client libraries such as ADO.Net or ODBC to access the database in Azure SQL Database. This option is useful when you want to leverage high availability and scaling, SQL Database offers. When you move your database to the Cloud, the functionality of the SQL Server database will not change except for some changes in Transact-SQL and login management. It is important to consider the network latency which you may experience between SQL Database and the application which is running on-premise.
In the second scenario, application is hosted in Azure and database also resides in Azure SQL Database. As shown in Figure, Application uses the same client libraries (as in the first scenario) to access the database in Azure SQL Database. Hosting your application in Azure boosts the performance of the application because network latency is minimized.
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