userid | personID | positionID
712 | 912 | 8
713 | 814 | 15
516 | 811 | 9
712 | 912 | 9
713 | 814 | 15
from the above table i have to find out userID of the person who has different multiple postion. i.e my query should return userID=712 because the user has 2 different positions.
Honestly i don't how to start
Any help will be really appreciaited