Sample data

Let's define two RowSets: @a and @b. Notice that both RowSets have duplicate rows.

@a  =
    SELECT * FROM
        (VALUES
            (1,    "Smith"),
            (1,    "Smith"),
            (2,    "Brown"),
            (3,    "Case")
        ) AS D( DepID, DepName );

@b  =
    SELECT * FROM
        (VALUES
            (1,    "Smith"),
            (1,    "Smith"),
            (1,    "Smith"),
            (2,    "Brown"),
            (4,    "Dey"),
            (4,    "Dey")
        ) AS D( DepID, DepName );