How prevent hack database

Yes of course
My app is competition with score
In this app,all user add code in app and if code is exist in database,so we give score for user
And in end,for users who have high score,we give gift(iphone) for his/him
This code inserted in database about 1 million records
Now if hacker hack my database and can get all code,so he/she can give all code for user and we will go away
Is it enough?