Using Merge in SQL Server 2008 R2

  --To Merge Data of different tables we can use merge statement in sql which first checks the content of both the tables and adds the data in the Target table which are missing from Soucre Table.

Syntax:

MERGE INTO [TARGETTABLE] AS Target
    USING [SOURCETABLE] AS SOURCE
    ON
        --unique key filtering condition
        Target.COLUMN1=SOURCE.COLUMN1 AND
        Target.COLUMN2=SOURCE.COLUMN2 AND
        Target.COLUMN3 =SOURCE.COLUMN3 AND
        Target.COLUMN4 =SOURCE.COLUMN4
     WHEN MATCHED THEN
        --update or delete query
        UPDATE SET
            Target.ColumnA=SOURCE.ColumnA,
            Target.ColumnB=SOURCE.ColumnB,
            Target.ColumnC=SOURCE.ColumnC

    WHEN NOT MATCHED THEN
        --INSERT QUERY
        INSERT (COLUMNA, ColumnB, ColumnC, ColumnD)
        VALUES(
                        SOURCE.ColumnA,
                        SOURCE.ColumnB,
                        SOURCE.ColumnC,
                        SOURCE.ColumnD                    )
    ;