mysql根据一张表更新另一张表数据

UPDATE channelcountry,
appywproducts 
SET channelcountry.ChannelName = appywproducts.YWNameCN 
WHERE
    channelcountry.ChannelCode = appywproducts.YWCode;

或者

UPDATE channelcountry a 
SET ChannelName = ( SELECT YWNameCN FROM appywproducts b WHERE a.ChannelCode = b.YWCode LIMIT 1 );

（完）