更新多条数据

UPDATE UT_ProductStock SET Stock =list.Stock-list.num
FROM (
    SELECT
        UT_ProductStock.PKID,
        UT_ProductStock.Stock,
        #temp.num
    FROM UT_ProductStock INNER JOIN #temp ON UT_ProductStock.PKID=#temp.PKID
    )AS list
WHERE list.pkid=UT_ProductStock.PKID