之前，同事在编写视图的过程中遇到这样了这个错误。我把简化后的语句整理如下：
1: select
as nf,
3: qxdm,
as csydmj--单位转换，2位小数
'城市'
6: group by m.qxdm order by m.qxdm
7:
8: union all
9:
10: select
as nf,
12: qxdm,
as csydmj--单位转换，2位小数
'城市'
15: group by n.qxdm order by n.qxdm