.
└── Universe
├── galaxy
│ ├── galaxy_id (type = SEQUENCE) -> primary key
│ ├── name (type = VARCHAR(40))
│ ├── mass_in_bill_earth_mass
│ ├── satellite_galaxy (type = BOOL)
│ └── humans_galaxy (type = BOOL)
├── star
│ ├── galaxy_id (type = INT) -> foreign key
│ ├── star_id (type = SEQUENCE) -> primary key
│ ├── name (type = VARCHAR(40))
│ ├── planets (type = INT)
│ ├── moons (type = INT)
│ ├── humans_star (type = BOOL)
│ ├── binary_star (type = BOOL)
│ └── age_in_bill_years (type = numeric(4,1))
├── planet
│ ├── galaxy_id (type = INT) -> foreign key
│ ├── star_id (type = INT) -> foreign key
│ ├── planet_id (type = SEQUENCE) -> primary key
│ ├── name (type = VARCHAR(40))
│ ├── humans_planet (type = BOOL)
│ ├── moons (type = INT)
│ ├── habitable (type = BOOL)
│ └── mass_in_earth_mass (type = numeric(4,1))
└── moon
├── galaxy_id (type = INT) -> foreign key
├── star_id (type = INT) -> foreign key
├── planet_id (type = INT) -> primary key
├── moon_id (type = SEQUENCE) -> primary key
├── name (type = VARCHAR(40))
├── habitable (type = BOOL)
├── mass_in_earth_mass (type = numeric(4,1))
├── milky_way_moon (type = BOOL)
└── shape (type = TEXT)