SQL怎么将字段B写入值为空的字段A答:假设您的空白字段为NULL(空值):update tablename set field1=isnull(a.field1,tablename.field1),field2=isnull(a.field2,tablename.field2),field3=isnull(a.field3,tablename.field3),field4=isnull(a.field4,tablename.field4),field5=isnull(a.field5,tablename.field5),field6=is...