有没有办法向已经存在的表中添加额外的列？例如，添加额外的列user，对于所有行和列date都为null设置为2015-02-01serial:long,title:chararray,year:int,score:float(49586,WinterWonderland,2013,2.8)(49587,TopGear:Series19:AfricaSpecial,2013,3.1)(49588,FireplaceForYourHome:CracklingFireplacewithMusic,2010,7.3)grunt>serial:long,title:chararray,year: