I'm just getting started on an intro to databases course and have a question about writing relational algebra expressions.


Person ( name, age, gender )
Frequents ( name, pizzeria )
Eats ( name, pizza )
Serves ( pizzeria, pizza, price )

I have a practice question like such: Find all pizzerias that serve at least one pizza that Amy eats for less than $10.00.

My answer is: πpizzeria (σname = 'Amy' ^ price < $10 (Person ⨝ Serves))

A correct answer is: πpizzeria (σname = 'Amy' (Eats) ⨝ σprice < $10 (Serves))

I would like to know if these two are equivalent to each other, and if not, why not?

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