Table_1 (existing table)

=====================
Col_1 | Col_2 | Col_3
------|-------|------
  A   |   B   |   1
  B   |   A   |   1
  A   |   C   |   2
  C   |   A   |   2
  D   |   E   |   3
  E   |   D   |   3
=====================




Table_2 (desired result)

=====================
Col_1 | Col_2 | Col_3
------|-------|------
  A   |   B   |   1
  A   |   C   |   2
  D   |   E   |   3
=====================