-- Database schema
| people : People_ID [ INT ] primary_key , District [ TEXT ] , Name [ TEXT ] , Party [ TEXT ] , Age [ INT ] | debate : Debate_ID [ INT ] primary_key , Date [ TEXT ] , Venue [ TEXT ] , Num_of_Audience [ INT ] | debate_people : Debate_ID [ INT ] primary_key debate_people.Debate_ID = debate.Debate_ID , Affirmative [ INT ] debate_people.Affirmative = people.People_ID , Negative [ INT ] debate_people.Negative = people.People_ID , If_Affirmative_Win [ TEXT ] |
-- -- Show the names of people who have been on the negative side of debates at least twice.

SELECT T2.Name FROM debate_people AS T1 JOIN people AS T2 ON T1.Negative  =  T2.People_ID GROUP BY T2.Name HAVING COUNT(*)  >=  2;