Databricks Certified Data Engineer Associate Practice Questions: Delta Lake and Data Management Domain

Correct Answer: B

Explanation: The correct syntax to create a Delta Lake table in Databricks is 'CREATE TABLE USING DELTA'. Options A, C, and D do not represent the correct syntax for this operation.

Correct Answer: A

Explanation: Using time travel extensively can increase storage costs because it retains historical versions of data. Option B is incorrect because time travel does not inherently cause data loss. Option C is incorrect because time travel itself does not slow down queries; performance depends on other factors. Option D is incorrect as time travel does not require schema updates.

Correct Answer: B

Explanation: The MERGE operation in Delta Lake is primarily used to update and insert data based on specified conditions, effectively handling upserts. Option A is incorrect because MERGE does not combine tables. Option C is incorrect because MERGE is not used for removing duplicates. Option D is incorrect because MERGE does not involve backing up data.

Correct Answer: C

Explanation: The OPTIMIZE command in Delta Lake is used to compact small files into larger ones, which can improve read performance by reducing the number of files that need to be accessed. Option A, VACUUM, is used to remove old data files that are no longer needed. Option B, MERGE, is used to update and insert data. Option D, CLEAN, is not a Delta Lake command.

Correct Answer: B

Explanation: Delta Lake handles data versioning through a transaction log that records all changes made to the data. Option A is incorrect because Delta Lake does not create snapshots of the entire dataset. Option C is incorrect as Delta Lake does not store multiple copies of the data. Option D is incorrect because Delta Lake does not rely on external version control systems.

Correct Answer: B

Explanation: Schema Enforcement in Delta Lake helps maintain data quality by preventing data that does not match the schema from being written. Option A, Time Travel, allows access to historical data but does not prevent bad data. Option C, Data Caching, is for performance, not data quality. Option D, Data Lineage, tracks data origins and transformations but does not prevent bad data.

Correct Answer: B

Explanation: Data compaction in Delta Lake helps reduce the size of data files by merging smaller files into larger ones, improving storage efficiency and query performance. Schema enforcement, ACID transactions, and time travel serve different purposes.

Correct Answer: C

Explanation: Delta Lake uses snapshot isolation to ensure ACID transactions, which allows multiple readers and writers to operate simultaneously without interference. Option A, distributed locks, are not used in Delta Lake. Option B, write-ahead logs, are a concept from databases like HBase and are not used in Delta Lake. Option D, two-phase commit protocol, is a distributed transaction protocol not specifically used by Delta Lake.

Correct Answer: B

Explanation: Time Travel is a feature of Delta Lake that allows users to query previous versions of the data. This is useful for auditing and debugging. Option A, Schema Evolution, refers to the ability to change the schema of a table over time. Option C, Data Lineage, is about tracking data's origin and transformations, not retrieving past data states. Option D, Data Caching, is about storing data in memory for faster access, not related to historical data views.

Correct Answer: B

Explanation: The 'OPTIMIZE' command in Delta Lake is used to compact small files into larger ones, which improves query performance. Option A is incorrect as 'OPTIMIZE' does not affect storage capacity. Option C is incorrect because 'OPTIMIZE' does not delete data. Option D is incorrect because 'OPTIMIZE' does not update schemas.