MERGE in sql server 2008

MERGE in sql server 2008. Explain with an example

Merge statement allows a single statement for INSERT, DELETE and UPDATE a row that depends on a condition. The target table for certain operations is based on the results of join with a source table.

The following example illustrates the use of MERGE.
MERGE InventoryMaster AS invmstr
USING (SELECT InventoryID, Descr FROM NewInventory) AS src
ON invmstr. InventoryID = src. InventoryID
WHEN MATCHED THEN
        UPDATE SET invmstr.Descr = src.Descr
WHEN NOT MATCHED THEN
INSERT (InventoryID, Descr) VALUES (src. InventoryID, src.Descr);.
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