在SQL中组合常见值

Question

说实例我有下表（成员之间充满了连接）

connectionA    ConnectionB
   887             225
   129             887
   225             887
   887             562
   562             887

如何使用SQL查找A连接到B的所有行，反之亦然。查询将返回（不允许重复）：

connectionA    ConnectionB
   887             225
   887             562

Answer 1

SELECT T1.connectionA, T1.connectionB
FROM yourtable T1
JOIN yourtable T2
ON T1.connectionA = T2.connectionB
AND T2.connectionA = T1.connectionB
WHERE T1.connectionA > T1.connectionB