TheMERGEstatement, also known asUPSERT, combinesINSERT, UPDATE, and DELETEoperations into asingle statementbased on a given condition. It is commonly used indata warehouses and large-scale databases.
Example Usage:
sql
MERGE INTO Employees AS Target
USING NewEmployees AS Source
ON Target.ID = Source.ID
WHEN MATCHED THEN
UPDATE SET Target.Salary = Source.Salary
WHEN NOT MATCHED THEN
INSERT (ID, Name, Salary) VALUES (Source.ID, Source.Name, Source.Salary);
If a match is found, the UPDATE clause modifies the existing record.
If no match is found, the INSERT clause adds a new record.
Why Other Options Are Incorrect:
Option A (INTO) (Incorrect):Used in INSERT INTO, butdoes not combine operations.
Option B (JOIN) (Incorrect):Used to combine rows from multiple tables, butnot for merging data.
Option D (DROP) (Incorrect):Deletes database objects liketables, views, and indexes, butdoes not merge data.
Thus, the correct answer isMERGE, as itcombines inserts, updates, and deletes into a single operation.
