sql语句的执行顺序

[NEW1981]

select top 10 id from a order by id desc是怎么执行的？

先选出top 10结果集来再对排序还是先对表中记录排序再选出top 10？

表a
id
1
2
3
...

15
select top 10 id from a order by id desc的结果怎么会是
15
14
13
。。。
6

真是莫名其妙了

[Limpire]

先 order by 再 top 10

[晓风残月0110]

在所属select的语句中先执行排序，之后周十佳

[elvis_gao]

select top 10 id from a order by id desc
/*上面是先排序后再取前10条，如果下面是先正序取10，再倒序排序，如果去掉里面的order by id ASC，则也是先排序后再取前10条*/
select * from (select top 10 * from @A order by id ASC) as A order by A.id  desc

[netmcuser]

先Order by，再select

[Limpire]

要得到10至1的数据：

select id from
	(
		select top 10 id from a order by id
	) as a
order by id desc

[Limpire]

declare @A table(id int)
insert @A
select 1 union all
select 2 union all
select 3 union all
select 4 union all
select 5 union all
select 6 union all
select 7 union all
select 8 union all
select 9 union all
select 10 union all
select 11 union all
select 12 union all
select 13 union all
select 14 union all
select 15

select * from
	(
		select top 10 * from @A-- order by id
	) as a
order by id desc

/*
id
10
9
8
7
6
5
4
3
2
1
*/

[Limpire]

里面的 order by id 不能被注释，注释后会得到15至6数据。

[pt1314917]

select top 10 id from a order by id desc

先排序后取前10条。。

[cxmcxm]

先排序后再取前10条