|   column   |  pk |     type     |
+------------+-----+--------------+
| id         | yes | int          |
| type       | yes | enum         |
| c_date     |     | date         |
| qty        |     | int          |
| combine_id |     | varchar(255) |

|  id | type |    date    | qty  |     combined_id     |
+-----+------+------------+------+---------------------+
| 001 | CB04 | 2015-01-01 |  700 | 001_CB04_2015-01-01 |
| 155 | AB01 | 2015-01-01 |  500 | 155_AB01_2015-01-01 |
| 300 | AB01 | 2015-01-01 | 1500 |                     |

select id
    , type
    , date
    , qty
    , id::text || '_' || type::text || '_' || date::text as combined_id
from your_table