試しにChatGPTに設計サンプル出してもらったら概ね>>124の形で出てきた
要件をもっと細かく伝えればたたき台としてなら実用可能なものを作ってくれそう

Users: user_id(PK), username, email, password, other user-related fields
MembershipRanks: rank_id(PK), rank_name, rank_description, annual_fee
RankConditions: condition_id(PK), rank_id(FK to MembershipRanks), condition_description, min_purchases
RankBenefits: benefit_id(PK), rank_id(FK to MembershipRanks), benefit_description, increased_points, discount_percentage, free_shipping_enabled
UserMembership: user_id(FK to Users), rank_id(FK to MembershipRanks), acquired_date, expiration_date