CREATE TABLE table_203_7 (id DECIMAL, "pos." DECIMAL, "artist" TEXT, "single" TEXT, "year" DECIMAL, "sales" DECIMAL, "peak" DECIMAL)

what is the difference in sales from the highest sales to the lowest sales ?
SELECT MAX("sales") - MIN("sales") FROM table_203_7
SELECT MAX("sales") - MIN("sales") FROM "table_203_7"