Databricks Certified Data Engineer - Associate
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In which of the following scenarios should a data engineer use the MERGE INTO command instead of the INSERT INTO command?
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KKeng
A
When the location of the data needs to be changed
B
When the target table is an external table
C
When the source table can be deleted
D
When the target table cannot contain duplicate records
E
When the source is not a Delta table
Explanation:
The MERGE INTO command (also known as UPSERT) is specifically designed for handling scenarios where you need to update existing records and insert new ones in a single operation. This is particularly important when the target table cannot contain duplicate records, as MERGE INTO allows you to:
- Update existing records when a match is found based on specified conditions
- Insert new records when no match is found
- Delete records (optional) when certain conditions are met
Why other options are incorrect:
- A: Changing data location is typically handled by ALTER TABLE or CREATE TABLE AS SELECT commands, not MERGE INTO.
- B: External tables can be targets for both INSERT INTO and MERGE INTO operations.
- C: Source table deletion is not a determining factor for choosing MERGE INTO vs INSERT INTO.
- E: MERGE INTO works with various source types, not just Delta tables.
Key takeaway: Use MERGE INTO when you need to handle upsert operations (update existing records and insert new ones) to maintain data integrity and prevent duplicates in the target table.
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