SAS：删除已出现值的行

我有一个包含两列ID的数据集，ID_a和ID_B。每行包含两个我认为属于同一个人的ID。因此，每个组合显示两次。例如：

ID_A   ID_B
A      B
C      D
B      A
D      C

我想要的是消除重复。也就是说，如果我有A，B行，我不需要B，A行

ID_A   ID_B
A      B
C      D

知道如何在SAS中执行此操作吗？

这个如何

data have;
   input (ID_A ID_B)($);
   cards;
A      B
C      D
B      A
D      C
;;;;
   run;
data haveV / view=haveV;
   set have;
   call sortc(of id:);
   run;
proc sort nodupkey out=want;
   by id:;
   run;
proc print;
   run;

这个怎么样

data have;
   input (ID_A ID_B)($);
   cards;
A      B
C      D
B      A
D      C
;;;;
   run;
data haveV / view=haveV;
   set have;
   call sortc(of id:);
   run;
proc sort nodupkey out=want;
   by id:;
   run;
proc print;
   run;

我喜欢@data-null-answer，它完美而健壮。您还可以尝试proc sql，如下所示

    proc sql;
    create table want as 
    select distinct
    case when ID_A le ID_B then ID_A else ID_B end as ID_A,
    case when ID_A ge ID_B then ID_A else ID_B end as ID_B
    from have;

我喜欢@data-null-answer，它完美而健壮。您还可以尝试proc sql，如下所示

    proc sql;
    create table want as 
    select distinct
    case when ID_A le ID_B then ID_A else ID_B end as ID_A,
    case when ID_A ge ID_B then ID_A else ID_B end as ID_B
    from have;