CREATE TABLE branch (branch_id DECIMAL, name TEXT, open_year TEXT, address_road TEXT, city TEXT, membership_amount TEXT)
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 purchase (member_id DECIMAL, branch_id TEXT, year TEXT, total_pounds DECIMAL)

Show member names without any registered branch.
SELECT name FROM member WHERE NOT member_id IN (SELECT member_id FROM membership_register_branch)
SELECT "name" FROM "member" WHERE NOT "member_id" IN (SELECT "member_id" FROM "membership_register_branch")