CREATE TABLE purchase (member_id DECIMAL, branch_id TEXT, year TEXT, total_pounds DECIMAL)
CREATE TABLE membership_register_branch (member_id DECIMAL, branch_id TEXT, register_year TEXT)
CREATE TABLE member (member_id DECIMAL, card_number TEXT, name TEXT, hometown TEXT, level DECIMAL)
CREATE TABLE branch (branch_id DECIMAL, name TEXT, open_year TEXT, address_road TEXT, city TEXT, membership_amount TEXT)

What are the opening years in which at least two shops opened?
SELECT open_year FROM branch GROUP BY open_year HAVING COUNT(*) >= 2
SELECT "open_year" FROM "branch" GROUP BY "open_year" HAVING COUNT(*) >= 2