Databricks Data Engineer Associate Question 349
Select 2A data engineer is using the COPY INTO command to load data from a Delta table into another Delta table. However, no data is being duplicated in the target table despite running the statement multiple times. What could be the reason for this behavior?
- A
The COPY INTO command uses the 'MERGE' functionality to avoid duplicating data by default.
- B
The target table already contains the files being copied, and COPY INTO skips files that are already present.
- C
The COPY INTO command is configured with an 'overwrite' option, which replaces existing data in the target table.
- D
The COPY INTO command writes metadata about loaded files to prevent re-ingestion of the same files.
- E
The schema of the source and target tables is incompatible, so the data is not being written.
Show answer and explanation
Correct answers: B, D
Explanation
The COPY INTO command is designed to avoid duplicating data by tracking the files that have already been ingested into the target table. If the same files are reprocessed, the command will skip them to maintain data integrity. Additionally, COPY INTO uses metadata to track previously loaded files, ensuring that duplicate data ingestion does not occur.
- A. Incorrect.
Incorrect. The COPY INTO command does not perform a 'MERGE'; it is used for appending new data or loading data from files.
- B. Correct.
Correct. COPY INTO tracks the files being ingested and skips files that have already been copied into the target table.
- C. Incorrect.
Incorrect. The COPY INTO command does not include an 'overwrite' option. Overwriting data would require a different approach, such as using a Delta overwrite operation.
- D. Correct.
Correct. COPY INTO maintains metadata about previously loaded files to prevent duplication during subsequent executions.
- E. Incorrect.
Incorrect. If the schema of the source and target tables were incompatible, COPY INTO would throw an error, not silently skip the data.