SELECT c.*,d.库存商品数,c.销售商品数/d.库存商品数 AS 动销率
FROM (#各城市各月销售商品数
    SELECT b.城市,b.年月,COUNT(b.商品ID) AS 销售商品数
    FROM (
        SELECT a.city AS 城市,a.`productID` AS 商品ID,DATE_FORMAT(a.`order_date`,"%Y%m") AS 年月
        FROM `test_a03order` AS a#订单表
        GROUP BY a.city ,a.`productID` ,DATE_FORMAT(a.`order_date`,"%Y%m")
    ) AS b
    GROUP BY b.城市,b.年月
) AS c
LEFT JOIN (#各城市各月库存商品数
    SELECT b.城市,b.年月,COUNT(b.商品ID) AS 销售商品数
    FROM (
        SELECT a.city AS 城市,a.`productID` AS 商品ID,DATE_FORMAT(a.`date`,"%Y%m") AS 年月
        FROM `test_a05order` AS a#库存表
        GROUP BY a.city ,a.`productID` ,DATE_FORMAT(a.`date`,"%Y%m")
    ) AS b
    GROUP BY b.城市,b.年月
) AS d ON c.城市=d.城市 AND c.年月=d.年月