select a.字段1,a.字段2,a.字段3,b.字段1,b.字段2,b.字段3 from 表1 as a 表2 as b where a.字段1='' or b.字段1='' and a.字段2=b.字段3

看懂里 你也是高手

select a.DiggID,a.DiggTime,a.diggnum,b.QQ,b.UserID,b.UserName from KS_Digg as a KS_User as b order by diggnum DESC