Recently Microsoft announced the release of the Release Candidate 0 for SQL Server 2025.
I’m running it locally, you can get the EXE from the Public Preview Download page.
I’ve posted previously on the new T-SQL features for this version.
I had put together a script to demonstrate the new T-SQL features in 2025, everything in the script still runs on RC 0.

PREVIEW_FEATURES:
One new thing added in RC 0 is a PREVIEW_FEATURES database configuration option. Turning this on will allow access to features that aren’t deemed ready to be added for a release, but are still available for use for evaluation.
Here’s an article with a few of the preview features listed.

You can run this SQL to enable the option:

ALTER DATABASE SCOPED CONFIGURATION SET PREVIEW_FEATURES = ON;

Alternatively, you can go into the properties of a database, select configurations, then set PREVIEW_FEATURES to ON.

Example:
One of the preview features is to create and index on a column using the vector datatype, CREATE VECTOR INDEX.

Here’s the code from my 2025 features script to create a table using the vector datatype. We can’t create a vector index on a temp table, and our table needs an integer primary key, so those adjustments were made. The CREATE VECTOR INDEX statement will fail, unless we enable PREVIEW_FEATURES.

DROP TABLE IF EXISTS dbo.VectorExample;

CREATE TABLE dbo.VectorExample(
	Id INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
	VectorValue VECTOR(5) NOT NULL
);

INSERT INTO dbo.VectorExample(VectorValue)
VALUES ('[1, 2, 3, 4, 5]');

INSERT INTO dbo.VectorExample(VectorValue)
VALUES (JSON_ARRAY(6, 7, 8, 9, 10));

SELECT * FROM dbo.VectorExample;

CREATE VECTOR INDEX ixVectorExample 
ON dbo.VectorExample(VectorValue)
WITH (metric = 'cosine', type = 'diskann');

GO

Links:

Brent Ozar – SQL Server 2025 RC0 Is Out

SQL Fingers: Breaking Changes & Migration Risks in SQL Server 2025