CREATE TABLE party (Party_ID VARCHAR, Party VARCHAR)
CREATE TABLE election (Committee VARCHAR, Party VARCHAR)

Which committees have delegates from both democratic party and liberal party?
SELECT T1.Committee FROM election AS T1 JOIN party AS T2 ON T1.Party = T2.Party_ID WHERE T2.Party = "Democratic" INTERSECT SELECT T1.Committee FROM election AS T1 JOIN party AS T2 ON T1.Party = T2.Party_ID WHERE T2.Party = "Liberal"
SELECT "T1"."Committee" FROM "election" AS "T1" JOIN "party" AS "T2" ON "Democratic" = "T2"."Party" AND "T1"."Party" = "T2"."Party_ID" INTERSECT SELECT "T1"."Committee" FROM "election" AS "T1" JOIN "party" AS "T2" ON "Liberal" = "T2"."Party" AND "T1"."Party" = "T2"."Party_ID"