LFC Data Management 2 — Questions and Answers
Question 1: Which Delta Lake feature enables you to travel back to a previous version of a table to correct a data error?
- Schema evolution
- Time Travel (Correct answer)
- Z-Ordering
- Liquid Clustering
Correct answer: Time Travel
Delta Lake's Time Travel feature allows querying or restoring a table to any prior snapshot using a version number or timestamp.
Question 2: In a lakehouse, what does the term 'schema enforcement' primarily prevent?
- Duplicate rows from being written
- Data that doesn't match the defined schema from being inserted (Correct answer)
- Queries from reading incorrect partitions
- Metadata from being cached incorrectly
Correct answer: Data that doesn't match the defined schema from being inserted
Schema enforcement (schema validation) rejects writes whose column types or names don't conform to the table's declared schema.
Question 3: What is the primary purpose of the Delta Lake transaction log (_delta_log)?
- Store raw Parquet data files
- Record every change to a Delta table as an ordered series of atomic commits (Correct answer)
- Cache query results for faster reads
- Maintain column statistics for Z-Ordering
Correct answer: Record every change to a Delta table as an ordered series of atomic commits
The _delta_log directory holds JSON and Parquet checkpoint files that form an ordered audit trail of all table operations.
Question 4: A data engineer wants to merge new customer records into an existing Delta table, updating existing rows and inserting new ones. Which SQL operation should they use?
- INSERT OVERWRITE
- COPY INTO
- MERGE INTO (Correct answer)
- CREATE OR REPLACE TABLE
Correct answer: MERGE INTO
MERGE INTO (upsert) matches source rows to target rows on a key and performs combined insert/update/delete actions in one atomic operation.
Question 5: Which data management practice in the lakehouse architecture keeps old, unreferenced data files from accumulating and consuming storage?
- Checkpointing
- VACUUM (Correct answer)
- OPTIMIZE
- Z-Ordering
Correct answer: VACUUM
The VACUUM command removes data files no longer referenced by the Delta transaction log and older than the retention threshold.
Question 6: What does 'data lineage' refer to in the context of lakehouse data management?
- The physical layout of Parquet files on cloud storage
- The chronological record of where data originated and how it transformed over time (Correct answer)
- The process of partitioning data by date columns
- The indexing strategy applied to large tables
Correct answer: The chronological record of where data originated and how it transformed over time
Data lineage tracks a dataset's origin, movement, and transformations, which is critical for governance, debugging, and regulatory compliance.
Question 7: In Unity Catalog, which object represents the highest level of the three-level namespace hierarchy?
- Schema
- Catalog (Correct answer)
- Table
- Volume
Correct answer: Catalog
Unity Catalog uses a three-level namespace: Catalog > Schema (database) > Table/View/Volume, with the catalog at the top.
LFC Data Management 2
Which Delta Lake feature enables you to travel back to a previous version of a table to correct a data error?