SQL Server 2025 Takes Shape with Release Candidate 0

ByHazem Yasser

SQL Server 2025 Takes Shape with Release Candidate 0

After months of private and public previews, Microsoft has officially released SQL Server 2025 Release Candidate 0 (RC0) — a pivotal milestone on the road to general availability later this year. First introduced in private preview in November 2024, followed by a broader public preview in May 2025, SQL Server 2025 is now entering a more stable phase, signaling that the final release is on the horizon.

This isn’t just another test build — RC0 gives developers, DBAs, and IT teams a realistic preview of what’s coming, with most core features locked in and ready for real-world evaluation.

🔧 New Preview Mode Lets You Test Experimental Features

One of the standout additions in RC0 is a new database-scoped configuration called PREVIEW_FEATURES. This setting allows enthusiasts and early adopters to enable experimental capabilities without affecting system stability.

Think of it as a “developer mode” for SQL Server — you can toggle on upcoming features, test them in isolated environments, and provide feedback before they go mainstream.

🤖 AI Takes Center Stage in SQL Server 2025

As expected, AI-driven enhancements are a major focus in this release — continuing Microsoft’s push to make SQL Server a smarter, more intelligent data platform.

With PREVIEW_FEATURES enabled, developers can now:

  • Create vector indexes using CREATE VECTOR INDEX
  • Run vector similarity searches directly in the database

These capabilities lay the groundwork for semantic search, retrieval-augmented generation (RAG), and AI-powered analytics — all within the familiar SQL environment.

Microsoft has also introduced:

  • AI_GENERATE_CHUNKS: Automatically splits text into smaller segments for vectorization.
  • CREATE EXTERNAL MODEL: Supports importing ONNX models directly into SQL Server for inference.

💡 Bonus: The sys.vector_indexes view now inherits columns from sys.indexes, ensuring consistent naming and easier querying for administrators.

And for macOS users running SQL Server via Docker or Rosetta 2 — yes, you can now leverage vector operations too, thanks to improved compatibility through the translation layer.

⚙️ Performance Gains with Intra-Query Parallelism

A highly anticipated under-the-hood improvement is intra-query parallelism with hyperthreading support. This enhancement allows individual queries to better utilize multi-core processors, especially on systems with hyperthreaded CPUs.

The result? Faster execution times for complex analytical workloads and large data scans — a big win for data-heavy applications.

🔐 Security and Encryption: Now the Default

Security remains a top priority, and SQL Server 2025 RC0 makes strong encryption the default behavior across key components:

  • TLS 1.3 is enabled by default for all connections.
  • TDS 8.0 support ensures modern, secure communication.
  • SQL Server Agent and Linked Servers now require encryption (Encrypt=Strict).
  • Replication uses OLE DB v19 and enforces TLS 1.3.
  • Always On Availability Groups, Failover Cluster Instances (FCI), log shipping, and replication all support TLS 1.3 configuration.

This shift reflects Microsoft’s commitment to zero-trust security models and compliance with modern data protection standards.

🐧 Linux Support Expanded: Ubuntu 24.04 Now Officially Supported

Good news for Linux users: Ubuntu 24.04 LTS (Noble Numbat) is now fully supported in SQL Server 2025 RC0. This ensures long-term stability and security updates for organizations running SQL Server on Linux in production environments.

🛠️ Other Notable Improvements and Fixes

Beyond the headline features, RC0 includes several quality-of-life and performance upgrades:

  • Time-bound Extended Events sessions now stop automatically when the specified duration ends — no more manual cleanup.
  • Cardinality Estimation (CE) Feedback for Expressions now persists across restarts and failovers, leading to more consistent query plans and reduced need for re-optimization.
  • PolyBase can now use managed identities to securely connect to Azure Blob Storage and Azure Data Lake Storage, simplifying authentication in cloud environments.
  • JARO_WINKLER_DISTANCE now returns float (was real) for better precision.
  • JARO_WINKLER_SIMILARITY returns int (was real) — aligning with expected output types.
  • REGEXP_REPLACE and REGEXP_SUBSTR now support LOB types (varchar(max), nvarchar(max)), making them more flexible for large text processing.
  • REGEXP_LIKE is now SARGable, meaning it can use indexes for faster execution — a major boost for query performance.
  • Resource governance is now available for Fabric Mirroring, helping isolate and manage resource usage.
  • A new dynamic maxtrans configuration option improves performance in Fabric mirroring scenarios.

📥 How to Download SQL Server 2025 RC0

Ready to test it out?
You can download SQL Server 2025 Release Candidate 0 now from the official Microsoft preview page:
👉 Download SQL Server 2025 RC0

⚠️ Reminder: RC0 is not for production use. It’s intended for testing, development, and feedback only.

📚 Want to Dig Deeper?

Check out the full release notes for detailed documentation on new features, breaking changes, and known issues:
👉 SQL Server 2025 RC0 Release Notes

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