BigQuery MERGE Statement – Explained

📘 What is BigQuery MERGE?

The MERGE statement in BigQuery allows you to conditionally INSERT, UPDATE, or DELETE rows in a target table based on matching rows from a source table. It’s ideal for data synchronization, staging table merges, and incremental updates.

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🧪 Syntax Overview

MERGE target_table AS T
USING source_table AS S
ON T.id = S.id
WHEN MATCHED THEN
  UPDATE SET T.name = S.name
WHEN NOT MATCHED THEN
  INSERT (id, name) VALUES (S.id, S.name);
      

🎯 Example Use Case

MERGE dataset.inventory AS I
USING dataset.new_arrivals AS N
ON I.product_id = N.product_id
WHEN MATCHED THEN
  UPDATE SET I.quantity = I.quantity + N.quantity
WHEN NOT MATCHED THEN
  INSERT (product_id, quantity) VALUES (N.product_id, N.quantity);
      

✅ Benefits of MERGE in BigQuery

• Atomic operations for INSERT, UPDATE, DELETE
• Efficient for large-scale ETL and staging workflows
• Reduces query complexity and improves maintainability

🔗 Related Posts

• MySQL MERGE Concept & Alternatives
• PostgreSQL MERGE & ON CONFLICT
• PostgreSQL ON CONFLICT Statement – Explained

📚 Stay tuned for more BigQuery tutorials and cloud data engineering tips from aki13promy.