CREATE TABLE shop (shop_id DECIMAL, address TEXT, num_of_staff TEXT, score DECIMAL, open_year TEXT)
CREATE TABLE member (member_id DECIMAL, name TEXT, membership_card TEXT, age DECIMAL, time_of_purchase DECIMAL, level_of_membership DECIMAL, address TEXT)
CREATE TABLE happy_hour_member (hh_id DECIMAL, member_id DECIMAL, total_amount DECIMAL)
CREATE TABLE happy_hour (hh_id DECIMAL, shop_id DECIMAL, month TEXT, num_of_shaff_in_charge DECIMAL)

What is the membership card held by both members living in Hartford and ones living in Waterbury address?
SELECT membership_card FROM member WHERE address = 'Hartford' INTERSECT SELECT membership_card FROM member WHERE address = 'Waterbury'
SELECT "membership_card" FROM "member" WHERE "address" = 'Hartford' INTERSECT SELECT "membership_card" FROM "member" WHERE "address" = 'Waterbury'