Foreign Key Constraints Behavior After Mirroring SQL Server to Fabric

Hi ShanthanPaladi ,

Yes, this is expected behavior. The Fabric mirroring process only replicates data — it does not carry over DDL schema objects like foreign key constraints from the source SQL Server. More importantly, the SQL Analytics Endpoint in Fabric is a read-only, auto-generated view over the underlying Delta/Parquet files in OneLake. Any schema-level changes you make directly on the SQL Analytics Endpoint (including manually adding foreign keys) can be lost or overridden when the mirroring sync refreshes the metadata or when the endpoint regenerates its schema.

This is a fundamental architectural difference from on-premises SQL Server. Fabric is an analytics platform, not a transactional one, and its constraint system is intentionally non-enforcing.

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Hello ShanthanPaladi 

This is expected behaviour. The mirrored database, available as a SQL analytics endpoint, is read-only. You are only allowed to analyze data in delta tables using a no code visual query editor or T-SQL to create views, functions, stored procedures, and apply SQL security - you can't apply DDL constructs!