Azure SQL Database is a cloud service from Microsoft that brings certain SQL Server functionalities to a cloud environment. This service is distinct from its on-premises counterpart, designed with specific adaptations and restrictions necessary for cloud compatibility.

Users can connect directly to Azure SQL Database within various products, eliminating the need for additional drivers. This straightforward connectivity is part of the service's configuration, simplifying access for users familiar with SQL Server's traditional setting.

Originally known as SQL Azure, the service transitioned to Azure SQL Database, reflecting its role within Microsoft's Azure cloud services. This change marked a broader shift as the service integrated more fully with the cloud environment, necessitating alterations to its features and operations.

A key operational aspect of Azure SQL Database is its focus on maintaining availability. The service automatically creates multiple replicas of databases to prevent data loss and minimize downtime. However, users can adjust resources, a feature intended to balance performance against demand, though this doesn’t guarantee the avoidance of throttling or resource-related limitations during high-traffic periods.

For those accustomed to SQL Server, Azure SQL Database supports T-SQL, allowing for various database management operations. Yet, there are notable omissions or modifications to certain system procedures and functions. These changes are due to the service's cloud-based structure, which imposes different security and performance management standards compared to traditional database environments.

Azure SQL Database does not replicate all features of SQL Server. It operates within a cloud setting where Microsoft manages certain administrative aspects, limiting some of the direct controls users might expect from an on-premises server. These limitations are inherent in the service's design, prioritizing cloud-readiness and systemic consistency over feature parity with standard SQL Server systems.

Adapting to Azure SQL Database from traditional SQL Server environments involves considering these cloud-specific changes. Users often face a period of adjustment, understanding the constraints and modified functionalities when operating their databases in the cloud. The service's structure underscores a shift in data management practices, aligning with a movement towards cloud-based resources.