在同一SQL语句中使用ORDER BY和UNION ALL

Question

这为什么不能给出预期的结果？

SELECT top 1 CITY, LEN(CITY) FROM STATION ORDER BY LEN (city) desc
union all 
SELECT top 1 CITY, LEN(CITY) FROM STATION ORDER BY LEN (city) asc;

Answer 1

您需要将每个有序查询表示为子查询，因为union无法跟随order by，因此：

select a.* from (select top 1 city, len(city) from station order by len(city) desc) a
union all 
select b.* from (select top 1 city, len(city) from station order by len(city)) b