$ echo test|awk '{$2 != ""? o="ABC" r="123" : o="123 r="ABC"}END{print "o:"o" r:"r}'
awk: cmd. line:1: {$2 != ""? o="ABC" r="123" : o="123 r="ABC"}END{print "o:"o" r:"r}
awk: cmd. line:1:                     ^ syntax error
awk: cmd. line:1: {$2 != ""? o="ABC" r="123" : o="123 r="ABC"}END{print "o:"o" r:"r}
awk: cmd. line:1:                                                         ^ syntax error
awk: cmd. line:1: {$2 != ""? o="ABC" r="123" : o="123 r="ABC"}END{print "o:"o" r:"r}
awk: cmd. line:1:                                                                ^ unterminated string
$

$ echo test|awk '{$1 != ""? o="ABC" : o="123"}END{print "o:"o}'
o:ABC
$ echo test|awk '{$2 != ""? o="ABC" : o="123"}END{print "o:"o}'
o:123