表table中有两个字段a和b,记录如下
a b
1 2
2 3
2 1
4 2
2 4
当统计记录数的时候第一行和第三行算一个记录,第四行和第五行算一个记录,就是如果某两行的a,b互换了的话算一行,当统计上面的数据条数时结果是3而不是5,请问怎样实现?

如果a，b本身不会有重复数据，可以尝试：select count(*) -(select count(*)/2 from 表名 aa,表名 bb where aa.a=bb.b and aa.b=bb.a) as sum_num
from 表名

select count(*)/2 from
(select a as i,b as j from test union select b as i,a as j from test) a

DECLARE @tb TABLE(a INT,b INT)
INSERT INTO @tb SELECT 1,2
UNION ALL SELECT 2,3
UNION ALL SELECT 2,1
UNION ALL SELECT 4,2
UNION ALL SELECT 2,4

SELECT COUNT(DISTINCT c)
FROM (SELECT a,b,c=a+b
FROM @tb) AS t