我想取一批学生基本信息中电话号码长度大于11位和为空的数据，我不想用or，用union
执行的时候报错，指向union ，如果 我不加insert into lw，后面语句执行都是正常的。麻烦大虾看看啥原因。
insert into lw
select * from (select first 1 a.id,a.ddtime from hf a,stu b where
a.stuid=b.stuid and a.ddtime between '03/01/2014' and '04/08/2014' and length(a.tel)>11)
union
select * from (select first 1 a.id,a.ddtime from hf a,stu b where
a.stuid=b.stuid and a.ddtime between '03/01/2014' and '04/08/2014' and a.tel='')
------解决方案--------------------
初步怀疑可能是：select * from (select first 1 a.id,a.ddtime from hf a,stu b where
a.stuid=b.stuid and a.ddtime between '03/01/2014' and '04/08/2014' and length(a.tel)>11)
union
select * from (select first 1 a.id,a.ddtime from hf a,stu b where
a.stuid=b.stuid and a.ddtime between '03/01/2014' and '04/08/2014' and a.tel='')这个查询出来的结果集跟目标表“lw”对应的列不匹配