Microsoft announces SQL Server 2025 Release Candidate 0

A private preview of SQL Server 2025 began in November 2024, followed by a public preview in May 2025. Now, it is time for the natural next step, as the tool has received its first release candidate, dubbed "RC0", bringing it one step closer to general availability, hopefully later in the year.

The highlight in this release is a new setting for enthusiasts, developers, and database administrators eager to try out experimental, upcoming features through a built-in PREVIEW_FEATURES database scoped configuration. You can find out more about how to leverage these capabilities through the release notes available here.

Other features include AI-focused enhancements, which are expected as Microsoft is focusing a lot in this area with SQL Server 2025. Developers can quickly create vector indexes and execute vector searches through the PREVIEW_FEATURES capability mentioned above. The company has also promised intra-query parallelism with hyperthreading, which should improve performance significantly. Microsoft has also empowered macOS developers to leverage vectors through the Rosetta 2 translation layer.

There are several other AI improvements in tow too. These include text chunking and ONNX model integration through the AI_GENERATE_CHUNKS and CREATE EXTERNAL MODEL features, both available through PREVIEW_FEATURES. In addition, sys.vector_indexes now inherits columns from sys.indexes, which means that it follows the same naming convention.

And as we highlighted yesterday, SQL Server 2025 RC0 supports Ubuntu 24.04 and enables TLS 1.3 by default. Here are some other, relatively smaller improvements too:

• Time-bound extended event sessions stop automatically after the specified time elapses.
• Cardinality Estimation (CE) Feedback for Expressions—cache persistence: Learns from repeated query patterns to pick better row estimates and plans. With persistence, that learning will survive restarts and failovers for steadier performance and less retuning.
• PolyBase now supports managed identity communications to Microsoft Azure Blob Storage and Microsoft Azure Data Lake Storage.
• JARO_WINKLER_DISTANCE returns float (previously real).
• JARO_WINKLER_SIMILARITY returns int (previously real).
• REGEXP_REPLACE and REGEXP_SUBSTR now support large object (LOB) types (varchar(max) and nvarchar(max)).
• REGEXP_LIKE is now SARGable, allowing index usage for faster query execution.
• SQL Server Agent, Linked Servers, defaults to encryption mandatory, using the latest security standards—TDS 8.0 and TLS 1.3.
• Configure TLS 1.3 encryption for Always On availability groups, failover cluster instances (FCI), replication, and log shipping with TDS 8.0 support.
• Replication defaults to OLEDB version 19 for inter-instance communication and enforces TLS 1.3 with Encrypt=Strict by default.
• Resource governance can now be used for Fabric Mirroring to isolate and manage resource consumption.
• Dynamic maxtrans configuration option to optimize Fabric mirroring performance.

If all of this interests you, you can download SQL Server 2025 RC0 from here.