Databricks Data Engineer Associate Question 396
Single answerWhile working with Delta Lake on Databricks, a data engineer attempts to write data into a table that has a NOT NULL constraint on one of its columns. However, the incoming data contains null values for this column. What is the default behavior when this constraint is violated?
- A
The write operation fails, and the transaction is rolled back.
- B
The null values are replaced with default values specified in the schema.
- C
The write operation succeeds, but a warning is logged.
- D
The write operation fails, but the transaction partially commits.
Show answer and explanation
Correct answer: A
Explanation
Delta Lake enforces schema constraints like NOT NULL strictly to ensure data quality and integrity. When such constraints are violated, the default behavior is to fail the write operation entirely and roll back the transaction. This ensures that no invalid data is written to the table.
- A. Correct.
This is correct. When a constraint violation occurs, such as a NOT NULL constraint being violated, Delta Lake's default behavior is to fail the write operation and roll back the transaction to maintain data integrity.
- B. Incorrect.
This is incorrect. Delta Lake does not automatically replace null values with default values unless explicitly configured using a default column value, which is not the default behavior.
- C. Incorrect.
This is incorrect. Delta Lake enforces constraints strictly, and violating a NOT NULL constraint does not allow the write to succeed with just a warning.
- D. Incorrect.
This is incorrect. Delta Lake enforces atomicity, which means if a constraint violation occurs, no part of the transaction is committed.