Question

A data engineer maintains a Silver customer table in Delta Lake. Each night a source extract arrives that contains both existing customers (already loaded) and brand-new customers. The business rule is strict: existing customer rows must NEVER be modified, but any customer not yet in the table must be inserted. Which MERGE statement correctly implements this requirement?

Accepted Answer

MERGE INTO silver_customers t USING updates s ON t.customer_id = s.customer_id WHEN NOT MATCHED THEN INSERT *

Answer

MERGE INTO silver_customers t USING updates s ON t.customer_id = s.customer_id WHEN MATCHED THEN UPDATE SET * WHEN NOT MATCHED THEN INSERT *

Answer

MERGE INTO silver_customers t USING updates s ON t.customer_id = s.customer_id WHEN MATCHED THEN DELETE WHEN NOT MATCHED THEN INSERT *

Answer

INSERT OVERWRITE silver_customers SELECT * FROM updates