sql选取重复的项

table1 id, bianhao,col,yj1, yj2, yj3, yj4
  1, 1, a1,NULL,NULL,意见,意见
  2, 1, a5,NULL,NULL,意见,意见
  3, 2, a3,NULL,NULL,意见,意见
  4, 2, a3,意见,意见,意见,意见
  5, 1, a1,意见,NULL,NULL,NULL
 现在就是bianhao,col 有重复的内容，想把它选出来怎么写，谢谢~！

SQL code

select * from table1 a
 where exists(select 1 from table1 where bianhao=a.bianhao and col=a.col and id<>a.id)