Select a subset of columns from a relation.
The Project operation, denoted by the Greek letter pi (π), is another fundamental unary operation in relational algebra. While the Select operation filters rows (horizontal subset), the Project operation selects a subset of attributes (columns), creating a vertical subset of the relation. The result of a Project operation is a new relation containing only the specified columns from the original relation. The format is π_(A1, A2, ..., An)(R), where 'R' is the relation and 'A1, A2, ..., An' is the list of attributes you want to keep. For instance, if we have a 'Students' relation with attributes 'student_id', 'name', 'major', and 'gpa', the operation π_(name, major)(Students) would create a new relation containing only the 'name' and 'major' columns for all students. An important property of the Project operation is that it automatically eliminates duplicate rows in the result. If multiple students have the same name and major, that combination will appear only once in the resulting relation. This is because relations in relational algebra are sets of tuples, and sets do not contain duplicates. The Project operation is equivalent to the `SELECT` column list in an SQL query, allowing us to specify exactly which pieces of information we are interested in for each record.