从图表数据中删除重复/循环

Question

我有图表数据，其中图表的弧（包括start [S]和end [E]）在关系表中存储如下：

IF OBJECT_ID('tempdb..#Test') IS NOT NULL DROP TABLE #Test;

CREATE TABLE #Test
(
    S NVARCHAR(1)   
    ,E NVARCHAR(1)
);

insert into #Test (S, E) values ('a', 'b');
insert into #Test (S, E) values ('b', 'a');
insert into #Test (S, E) values ('a', 'c');

因此图表由以下弧组成：

a -> b
b -> a
a -> c

我想删除重复项/周期：a - ＆gt; b和b - ＆gt; a =＆gt; a - ＆gt;湾这可能吗？

Answer 1

示例

;with cte as (
    Select *
          ,RN = Row_Number() over (Partition By case when S<E then S+E else E+S end order by s,e)
     From  #Test
)
Delete From cte Where RN>1

更新测试

S   E
a   b
a   c

Answer 2

如果你只是像你的例子那样得到简单的重复：

DELETE
FROM #test AS t1
WHERE EXISTS
 ( SELECT *
   FROM #test AS t2
   WHERE t1.S = t2.E -- there's the same S/E combination, but switched
     AND t1.E = t2.S
     AND t1.S > t2.S -- delete only one of the combinations
 )