What is the difference between Select and Project Operations

Question

I\'m referring to the basic relational algebra operators here.
As I see it, everything that can be done with project can be done with select.

I don\'t know if

Answer 1

The difference between the project operator (π) in relational algebra and the SELECT keyword in SQL is that if the resulting table/set has more than one occurrences of the same tuple, then π will return only one of them, while SQL SELECT will return all.