高分请教 SQL 查询语句

[tracy_go]

表中有字段 IDX(int)，FREQ(float)
现在有如下记录：
1,10
2,11.2
3,18.4
4,47.4
5,50.9
6,85.7
......

现在我已知 FREQ=18。想在数据库中找到与它最接近的值即18.4的IDX---3.
用SQL语句怎么实现？

[叶子]

declare @T table([IDX] int,[FREQ] float)
insert @T
select 1,10 union all
select 2,11.2 union all
select 3,18.4 union all
select 4,47.4 union all
select 5,50.9 union all
select 6,85.7

DECLARE @freq INT 
SET @freq=18

select TOP 1 * from @T ORDER BY ABS([FREQ]-@freq)
/*
IDX         FREQ
----------- ----------------------
3           18.4
*/

[lzw_0736]

WITH a1 (IDX,FREQ) AS
(
SELECT 1,10 UNION all
SELECT 2,11.2 UNION all
SELECT 3,18.4 UNION all
SELECT 4,47.4 UNION all
SELECT 5,50.9 UNION all
SELECT 6,85.7
)
SELECT TOP 1 IDX
FROM a1
ORDER BY ABS(FREQ-18) asc

[昵称90天可改一次]

蹭分万岁

create table test(idx int, freq float)
insert into test values(1,10)
insert into test values(2,11.2)
insert into test values(3,18.4)
insert into test values(4,47.4)
insert into test values(5,50.9)
insert into test values(6,85.7)
DECLARE @num float
set @num=18
select top 1 *
from test
group by idx,freq
order by MIN(abs(freq-@num))