Sql 在查询的Select子句中使用Distinct with Top

在SQL Server中，我可以创建在Select子句中同时使用Top和Distinct的查询，例如：

Select Distinct Top 10 program_name
From sampleTable

数据库将返回前10个结果中的不同值，还是返回前10个不同值的结果？这种行为在SQL中是一致的还是依赖于数据库？

使用

Select Top 10 program_name
From sampleTable group by program_name;

它将返回前10个不同的程序名。

您的查询还将返回不同的10程序名。

使用

Select Top 10 program_name
From sampleTable group by program_name;

它将返回前10个不同的程序名。

---

您的查询还将返回不同的10程序名。

TOP

最后执行，因此您的

distinct

首先运行，然后运行

TOP

---

TOP

最后执行，因此您的

DISTINCT

首先运行，然后运行

TOP

试试这个：

select distinct top 10 c from
(
    select 1 c union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 2
) as T
order by c

将该结果与以下查询进行比较：

select distinct c from (
    select top 10 c from
    (
        select 1 c union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 2
    ) as T
    order by c
) as T2

select top 10 c from (
    select distinct c from
    (
        select 1 c union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 2
    ) as T
) as T2
order by c

试试这个：

select distinct top 10 c from
(
    select 1 c union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 1   union all
    select 2
) as T
order by c

将该结果与以下查询进行比较：

select distinct c from (
    select top 10 c from
    (
        select 1 c union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 2
    ) as T
    order by c
) as T2

select top 10 c from (
    select distinct c from
    (
        select 1 c union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 1   union all
        select 2
    ) as T
) as T2
order by c