SQL Server在子查询中按最大行排序

Question

以下查询适用于PostgreSQL，我想知道为什么它不适用于SQL Server 2016。

select * from (values (1),(2)) as a(a)
UNION
(
  select * from (values (1),(2)) as a(a)
  order by 1 desc
  offset 0 rows fetch first 1 rows only
)
order by 1 desc offset 0 rows fetch first 1 rows only

谁能向我解释为什么不支持订购？

有趣的是，以下是另一种表达方式，它像一种魅力

select * from (values (1),(2)) as a(a)
where a.a in(
  select * from (values (1),(2)) as a(a)
  order by 1 desc
    offset 0 rows fetch first 1 rows only
)
order by 1 desc offset 0 rows fetch first 1 rows only

这是错误吗？

Answer 1

联合后的查询需要作为选择显示，如下所示：

select * from (values (1),(2)) as a(a)
UNION
select * from
(
select * from (values (1),(2)) as a(a)
order by 1 desc
offset 0 rows fetch first 1 rows only
) b
order by 1 desc offset 0 rows fetch first 1 rows only