create table tx1(
id int IDENTITY primary key,
x1 int,
x2 int)
go

Declare @i int=0
SELECT RAND(100)
WHILE @i <30000  
   BEGIN  
      Set @i=@i+1
      Insert into tx1 values(RAND()*10000000,RAND()*10000000)
   END; 

-- 45 sec
select * from tx1 t1
inner join tx1 t2 on(t1.x1=t2.x1 or t1.x2=t2.x2)  and t1.id!=t2.id

-- <1 sec
select * from tx1 t1
inner join tx1 t2 on(t1.x1=t2.x1)  and t1.id!=t2.id
union
select * from tx1 t1
inner join tx1 t2 on(t1.x2=t2.x2)  and t1.id!=t2.id