Fully normalized gym management system ERD in 3NF with 13 entities modeling members, memberships, trainers, classes, bookings, and equipment tracking. Data flows from Member through Membership and Payment entities, while Trainer and Employee hierarchies manage staff and class scheduling, with junction tables Membership_Type_Benefit and Trainer_Expertise resolving many-to-many relationships. This schema eliminates data redundancy and enforces referential integrity across member lifecycles, class attendance, and equipment usage. Fork and customize this diagram on Diagrams.so to adapt table structures, add indexes, or extend for billing and inventory features. The self-referencing Manager_ID in Employee enables organizational hierarchy modeling for gym staff chains of command.