需要SQL帮助

Question

下面是我的表的简化版本.

    FRID, RELFRID, Relationship
    123, 456, Husband/Wife
    456, 123, Wife/Husband
    345, 765, Brother/Sister
    765, 345, Sister/Brother

我想只拉一个关系的表示(只是每组两个记录中的一个).我尝试了很多东西,包括EXCEPT和SUBSELECTS,我尝试的所有东西都没有结果,因为左边的每个数字也表示在右边.知道如何获得我正在寻找的结果吗？我已经尝试了以下查询的每个组合.

    select frid, relfrid from frrelmst
    except
    select frid, relfrid from frrelmst
    where frid in (select relfrid from frrelmst)
    order by frid, relfrid

    Select frid, relfrid from frrelmst where 
    relfrid+frid not in (select frid+relfrid from frrelmst)

Answer 1

简单 :

select frid, relfrid from frrelmst where  frid < relfrid