Definition
Projection (Relational Algebra)
The projection operation
selects a subset of attribute from a relation and maps it to a new relation containing only those attributes, i.e. Where
is a new tuple containing only the values from the attribute specified in the list for a given tuple . Since the resulting relation is a set, any duplicate tuple that arise from this operation are automatically eliminated. Note that there’s also the possibility for extended projection, meaning specifying expressions instead of attributes, i.e.: