Oracle select, concatenate, deselect

Question

I have a field that a software vendor formatted strangely, and I need to format it a certain way on select
I use two case statements,
CASE(WHEN TRANS_NUM = ---- )"TIME_POSTED1"
CASE(WHEN TRANS_NUM = ----) "TIME_POSTED2"
- This works fine, but I need to return them as one Column, and eliminate the first two Columns,
so it would be TIME_POSTED1 || TIME_POSTED2 AS TIME_POSTED 
and "DESELECT" TIME_POSTED1,  TIME_POSTED2
How can I do this?