Question

SQLServer中如何查出数据库中百分比的数据

假定数据库名“test” 主键“ID” 查出30%的数据 条件是后面的30%数据

Answer 1

sql2005以后.优先使用如下方式，扩展性强。
---------------------------------------------------------------------
select A.* from
(
SELECT ROW_NUMBER() OVER(ORDER BY ID DESC) AS rownum ,B.*
FROM dbo.testB
) A
where A.rownum>=1 and A.rownum<=(select count(*)*3/10 from dbo.test)
---------------------------------------------------------------------
2000 数据库
SELECT TOP (select count(*)*3/10 from dbo.test) * FROM test order by ID DESC
----------------------------------------------------------

Answer 2

select top( select convert(int, (select count(*) from test)*0.3))* from test order by ID desc

Answer 3

1> SELECT
2> *
3> FROM
4> union_tab_2
5> go
id val
----------- ----------
1 A
1 A
2 B
4 D

(4 行受影响)
1> SELECT
2> TOP ((SELECT COUNT(1) FROM union_tab_2) * 3 / 10)
3> *
4> FROM
5> union_tab_2
6> go
id val
----------- ----------
1 A

(1 行受影响)