year competition venue position event notes
year
competition
venue
position
event
notes
number
address
number
number hour min sec
number text address rank text time
1994 european championships helsinki, finland 48th marathon 2:22:49
which four competitions are the only competitions that occurred once ?
WDT CD NNS VBD-AUX DT JJ NNS WDT VBD RB .
World Cross Country Championships|Helsinki Marathon|Fukuoka Marathon|Beppu-Ōita Marathon
select c2 from w group by c2 having count ( * ) = 1