Answer: Records that violate the expectation cause the job to fail.

## Explanation In Delta Live Tables (DLT), the `ON VIOLATION` clause determines how constraint violations are handled. The specific syntax used in the question is: ```sql CONSTRAINT valid_timestamp EXPECT (timestamp > '2020-01-01') ON VIOLATION FAIL UPDATE ``` The `ON VIOLATION FAIL` directive means that when any record violates the constraint, the entire job fails. This is a strict enforcement mechanism that ensures data quality by preventing any invalid data from being processed. ### Key Points: 1. **`ON VIOLATION FAIL`**: This is the critical part - it causes the pipeline to fail when constraints are violated. 2. **Comparison with other options**: - **Option A**: Incorrect - Records are not just dropped and logged; the job fails. - **Option B**: Correct - The job fails when violations occur. - **Option C**: Incorrect - This would be more appropriate for `ON VIOLATION DROP AND COUNT` or similar quarantine mechanisms. - **Option D**: Incorrect - Records violating constraints are not added to the target dataset. 3. **DLT Constraint Types**: - `ON VIOLATION FAIL`: Job fails on violation - `ON VIOLATION DROP ROW`: Violating rows are dropped - `ON VIOLATION DROP AND COUNT`: Violating rows are dropped and counted This behavior ensures data quality by enforcing strict validation before data enters the target dataset, which is crucial for production data pipelines.

Author: Keng Suppaseth