Merge

Description: One of the most exciting new features addressing the needs for ETL is the SQL statement MERGE. The new SQL combines the sequence of conditional INSERT and UPDATE commands in a single atomic statement, depending on the existence of a record. This operation is commonly known as Upsert functionality.

Syntax -
 
MERGE INTO bonuses b
USING (
  SELECT employee_id, salary, dept_no
  FROM employee
  WHERE dept_no =20) e
ON (b.employee_id = e.employee_id)
WHEN MATCHED THEN
  UPDATE SET b.bonus = e.salary * 0.1
  DELETE WHERE (e.salary < 40000)
WHEN NOT MATCHED THEN
  INSERT (b.employee_id, b.bonus)
  VALUES (e.employee_id, e.salary * 0.05)
  WHERE (e.salary > 40000);

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