Microsoft SQL Server is a relational database system. The current version is SQL Server 2025, available in editions such as Enterprise, Standard and Express, plus free developer editions. It runs on Windows and Linux, on-premises, in the cloud or in hybrid setups. It offers T-SQL, JSON, a vector data type, high availability through Always On, and security features such as Transparent Data Encryption, Always Encrypted and row-level security. Azure SQL Managed Instance is a Microsoft-managed variant with close to full compatibility with SQL Server.
Microsoft is headquartered in Redmond, Washington, and the software is proprietary. Organisations that host SQL Server themselves keep data on their own infrastructure. Managed Instance runs in a chosen Azure region; for Azure services in general, Microsoft states that customer data is not stored or processed outside the chosen geography without authorisation, with documented exceptions. Because Microsoft is a US company, SQL Server falls under US jurisdiction, including the CLOUD Act, which matters most for the managed variant.