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 there is a difference or a certain nuance that I've missed.

Answer 1

PROJECT eliminates columns while SELECT eliminates rows.

Answer 2

Select Operation : This operation is used to select rows from a table (relation) that specifies a given logic, which is called as a predicate. The predicate is a user defined condition to select rows of user's choice.

Project Operation : If the user is interested in selecting the values of a few attributes, rather than selection all attributes of the Table (Relation), then one should go for PROJECT Operation.

See more : Relational Algebra and its operations

Answer 3

In Relational algebra 'Selection' and 'Projection' are different operations, but the SQL SELECT combines these operations in a single statement.

Select retrieves the tuples (rows) in a relation (table) for which the condition in 'predicate' section (WHERE clause) stands true.

Project retrieves the attributes (columns) specified.

The following SQL SELECT query:

select field1,field2 from table1 where field1 = 'Value';

is a combination of both Projection and Selection operations of relational algebra.