select product_id,sku,original_price,current_price,on_markdown,original_price-current_price AS discount_amount, round(((original_price-current_price)/(original_price*1.00)),2) AS discount_pct from retail.products where on_markdown=1

Now that you have the discount_pct, use your code from that calculation and multiply it by the original_price to see if it matches the discount_amount you calculated . Again, do this calculation in a new column and name the column check.