Изменения

*Ограничение

check not HasScolarship or 60 <=

all (select Points from Points where Points.SId = Id)

*Запрос

**Оценки стипендиатов группы M34391 по СУБД

select Points from Students natural join Points

where HasScolarship and CId = 10 and GId = M34391

**$σ_{HasScolarship ∧ CId = 10}(Students ⋈ Points)$

*Оптимизированный запрос

**$σ_{GId=M34391 ∧ HasScolarship}(Students) ⋈⋈ σ_{60 ≥ Points ∧ CId = 10}(Points)$