SQL Server 2025: Quick Overview of All Changes

Edition-Related Changes

• The edition lineup itself is unchanged: Enterprise, Standard, Developer, Express, Web.
• Microsoft's stated direction for 2025 is to make the new AI capabilities (vector type, similarity search) available broadly rather than gating them to Enterprise only, so you can prototype AI features on Developer or Express and not hit a licensing wall on day one.
• Deeper platform integration (Microsoft Entra ID auth, Microsoft Defender for Cloud, Purview) increasingly assumes the instance is Azure Arc-enabled. Arc-enablement itself is free, but it's a prerequisite you'll want to plan for rather than discover during a security review.
• As always, confirm the current edition comparison chart before committing a specific feature to a specific edition; this is the area most likely to be adjusted between preview and GA servicing updates.

Built-In Artificial Intelligence Capabilities

The headline theme of the release: AI workloads move into the engine instead of living in a bolted-on vector store.

• Native VECTOR type stores embeddings directly on the row, next to the data they describe.
• VECTOR_DISTANCE ranks rows by cosine, Euclidean, or dot-product similarity.
• DiskANN-based approximate vector index makes similarity search scale past a full table scan.
• sp_invoke_external_rest_endpoint calls out to a model or scoring endpoint directly from T-SQL, without an application tier in between.
• Model Context Protocol (MCP) support lets SQL Server act as a structured data source for AI agents, so an agent can query your schema through a governed interface instead of raw connection strings.

Full walkthrough with code: SQL Server 2025: What's New for Developers and DBAs.

Development Features and Enhancements

Code examples for all of these: SQL Server 2025: What's New for Developers and DBAs.

DBA Features and Enhancements

• Optimized locking: fewer, shorter-lived locks, aimed at cutting blocking chains on busy OLTP systems.
• Intelligent Query Processing, extended again: more bad plans get fixed automatically instead of needing hand-tuned hints, at the usual cost that a few workloads need re-baselining after the compatibility level changes.
• Compatibility level floor moves up: SQL Server 2025 supports compatibility level 150 (SQL Server 2019) and newer. Databases sitting on 140 or lower need attention before or during migration, not after.
• Query Store continues to pick up refinements aimed at making regression hunting after an upgrade less manual.

Performance Enhancements

• Optimized locking and extended IQP (see above) are the two changes most likely to move the needle on an existing OLTP workload without any code change.
• Vector index build and query performance scale to larger tables via the DiskANN approximate index rather than forcing an exact, full-scan comparison.
• As with every release, "faster" is a workload-dependent claim. Some plans improve automatically under the new compatibility level, some regress and need attention. There is no substitute for a before/after baseline on your own queries.

High Availability and Disaster Recovery Improvements

• Continued refinement of Always On Availability Groups: faster automatic seeding and incremental hardening of the contained-availability-group model that keeps more instance-level metadata (logins, jobs, etc.) inside the AG itself instead of requiring separate synchronization.
• Distributed Availability Group tooling keeps maturing alongside the core engine changes.
• None of this changes the fundamentals: HADR design is still driven by RPO/RTO requirements, and a failover strategy is only as good as the last time it was actually tested.

Security Changes

• Microsoft Entra ID (Azure AD) authentication continues expanding on-premises, reducing the case for standing SQL logins.
• Managed identities cover outbound connections such as the REST endpoint calls used for AI scoring, so credentials don't have to live in T-SQL or a connection string.
• Tighter Microsoft Purview integration for data classification and audit, moving governance closer to being a property of the engine rather than a separate scanning pass.
• The operational rule hasn't changed: fewer standing secrets, more short-lived and auditable access. Run Invoke-sqmLoginAudit after any upgrade to confirm access hasn't silently drifted.

Microsoft Fabric Integration

• Fabric Mirroring for SQL Server is the other headline feature alongside AI: near real-time mirroring of operational data into Microsoft Fabric / OneLake.
• Analysts query a continuously updated copy in the lakehouse; production stays dedicated to transactions, no nightly ETL window, no heavy analytical queries competing with OLTP on the same box.
• This is the same mirroring model Azure SQL Database and Azure SQL Managed Instance already had, now extended to the boxed product running on your own hardware.

Discontinued Features

• Compatibility level floor: level 150 (SQL Server 2019) is the oldest level supported; anything on 140 or below needs to move up before or during the migration.
• Every release continues the multi-version phase-out already underway before 2025: Stretch Database and PolyBase-to-Hadoop connectivity remain removed, and R support in Machine Learning Services remains on its deprecation path in favor of Python.
• The reliable way to find out what specifically breaks in your databases is the Data Migration Assistant, not a generic list, run it against a copy of production before you commit to a date.

Where to Go Next

The Bottom Line

SQL Server 2025 splits cleanly into two headline moves (AI in the engine, Fabric mirroring for analytics) plus the steady, expected evolution everywhere else: a stricter compatibility floor, lighter locking, deeper Entra ID integration, and the usual short list of things quietly removed. None of it changes the upgrade discipline: baseline first, test on a copy, raise compatibility level as its own step, and keep a tested rollback ready.