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

List all open years when at least two shops are 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