選擇1條記錄，其中兩條記錄在不同列中具有相同的值

Question

我有一個包含兩列的表。

的前兩行的列值是反轉的，我將如何選擇適合每一個地方一個STATION_1_I等於另一個記錄STATION_2_I及其STATION_2_I等於STATION_1_I例如一個記錄

。

Answer 1

INTERSECT將刪除重複你

select "station_1_I", "station_2_I" from mytable 
intersect 
select "station_2_I", "station_1_I" from mytable 
      where "station_2_I" < "station_1_I" 

SQL Fiddle

Answer 2

select a,b from 
(
select 
(case when a<b then a else b end) as a, 
(case when a>b then a else b end) as b 
from (
select station_1_I as a, station_2_I as b from MyTable 
union all 
select station_2_I, station_1_I from MyTable 
) having count(*)=2 group by a,b 
) group by a,b