Foreign key constraint in a dlt pipeline

[Mario_D]

As primary/foreign key constraints are now supported/available in Databricks, how are foreign key constraints handled in a dlt pipeline, i.e if a foreign key constraint is violated, is the record logged as a data quality issue and still added to the target table?

[szymon_dybczak · Accepted solution]

Hi @Mario_D ,

I don't think primary/foreign constraint are supported by DLT. At least I can't find anything in documentation. But you obtain same result using DLT expectations:

Manage data quality with Delta Live Tables - Azure Databricks | Microsoft Learn

[RCo]

Hi @Mario_D!

While primary & foreign key constraints are generally available in Databricks Runtime 15.2 and above, they are strictly informational only.

This means that a primary key will not prevent duplicates from being added to a table and a foreign key does not require the referenced value to exist in another table.

https://docs.databricks.com/en/tables/constraints.html#declare-primary-key-and-foreign-key-relations...