Re: Small problem to solve

[Rick James]

SELECT `item name`, `qty buy` - `qty sold`
    FROM ( SELECT `item name`, SUM(`qty buy`) AS `qty buy`
               FROM csv1 GROUP BY `qty buy` )
    JOIN ( SELECT `item name`, SUM(`qty sell`) AS `qty sell`
               FROM csv2 GROUP BY `qty sell` )
       USING(`item name`);

However, that is not quite right since it lists only items for which there were both buys and sells. And it does not limit to the year. But maybe it will help you get started.