CREATE TABLE people (people_id NUMBER, district CLOB, name CLOB, party CLOB, age NUMBER)
CREATE TABLE debate_people (debate_id NUMBER, affirmative NUMBER, negative NUMBER, if_affirmative_win others)
CREATE TABLE debate (debate_id NUMBER, date CLOB, venue CLOB, num_of_audience NUMBER)

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
SELECT "T2"."name" FROM "debate_people" "T1" JOIN "people" "T2" ON "T1"."negative" = "T2"."people_id" GROUP BY "T2"."name" HAVING COUNT(*) >= 2