two select seperately works, but union them doesnot work
select TO_CHAR(timeentry,'YYYY-MM-DD') as mcdatefield from morningcheckreport
group by TO_CHAR(timeentry,'YYYY-MM-DD') order by mcdatefield
union
select TO_CHAR(timeentry,'YYYY-MM-DD') as acdatefield from alertcheckreport
group by TO_CHAR(timeentry,'YYYY-MM-DD') order by acdatefield
第一个不能有 order by .
查询结果没出来之前不能有order by
两个链接链接起来 观察结果什么时候出来的 再在后面加排序才行的.