Databricks Data Engineer Associate Question 338
Select 3You are working with a Delta table in Databricks that tracks customer orders. The table occasionally receives duplicate records when data is ingested from multiple sources. You decide to use the MERGE command to deduplicate the data. Which of the following steps must you include in your MERGE operation to ensure duplicates are removed correctly?
- A
Define a condition that matches records in the source and target based on a unique identifier.
- B
Use the DELETE clause in the MERGE statement to remove rows from the target table that are duplicates in the source.
- C
Use the WHEN MATCHED THEN UPDATE clause to update records in the target table with the latest values from the source.
- D
Use the WHEN NOT MATCHED THEN INSERT clause to add new records from the source to the target table.
- E
Include a DISTINCT keyword in the MERGE statement to automatically remove duplicates.
Show answer and explanation
Correct answers: A, C, D
Explanation
The MERGE command is highly effective for deduplication when writing to a Delta table. You need to define a matching condition based on a unique identifier (e.g., a primary key) to identify duplicates. The WHEN MATCHED THEN UPDATE clause ensures existing records in the target table are updated with the latest values, while the WHEN NOT MATCHED THEN INSERT clause ensures that only new records are added. The DISTINCT keyword is not part of the MERGE syntax, and the DELETE clause is not relevant for deduplication in this scenario.
- A. Correct.
Correct: A condition that matches records based on a unique identifier ensures that only corresponding records are updated or inserted, providing a foundation for deduplication.
- B. Incorrect.
Incorrect: The DELETE clause is not used for deduplication in a MERGE statement. Instead, it is used for other scenarios, like removing data based on specific conditions.
- C. Correct.
Correct: The WHEN MATCHED THEN UPDATE clause allows you to update existing records in the target table, ensuring that duplicates are replaced with the latest or most accurate values.
- D. Correct.
Correct: The WHEN NOT MATCHED THEN INSERT clause ensures that new, non-duplicate records are added to the target table.
- E. Incorrect.
Incorrect: The DISTINCT keyword is not valid within a MERGE statement and cannot be used to remove duplicates in this context.