SELECT "sales" FROM table_203_7 WHERE "single" = '"blue (da ba dee)"' AND "artist" = 'eiffel 65'
what were the total sales of eiffel 65 's blue -lrb- da ba dee -rrb- ?
CREATE TABLE table_203_7 (
    id number,
    "pos." number,
    "artist" text,
    "single" text,
    "year" number,
    "sales" number,
    "peak" number
)