Symbols for Relational Algebra Expressions and Other Symbols Symbols for relation schemas: R, S, T Symbols for relations: R, S, T, ∅ Symbols for Relational Algebra operators: ∪, -, π, σ, ρ, ⨯, ∩, Δ, ÷, ⨝, ⟗, ⟕, ⟖, ⋉, ⋊, ▷ Symbols for logical connectives: ∧, ∨, ¬ Symbols for comparison predicates: , =, ≤, ≥, ≠ Symbols for set-theoretical operations: ∈, ∉, ⊆, ⊂, ⊇, ⊃ Other mathematical symbols: ⊥, ⋅, ∃, ∀, ∘, ←, → All names (for example, for relations and attributes) should be written in normal font (no italics) to increase readability. All symbols should be surrounded by blanks to increase readability. Database schema Animals(AnimalID, Species, Name, DateOfBirth, Gender, HabitatID, Origin, ArrivalDate, DietType)Habitats(HabitatID, Type, Size, Location, CleaningSchedule, EnvironmentControlSettings)ZooStaff(StaffID, FirstName, LastName, Role, Department, HireDate, Qualifications, ContactNumber)AnimalHealthCare(StaffID, AnimalID, CareDate, Treatment, Notes)VisitorTours(TourID, Date, Time, GuideStaffID, RouteDescription, Theme, Duration, GroupSize)Maintenance(MaintenanceID, HabitatID, Description, Year, Date, StaffID, Status, Priority)ConservationPrograms(ProgramID, Name, Description, StartDate, EndDate, ResponsibleStaffID)ZooEvents(EventID, Name, Date, Time, Location, OrganizerStaffID, TargetAudience, Budget) Query Identify staff members (their names and roles) who have never organized an event, performed habitat maintenance, or provided health care to any animals.
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