The window clause allows the definition of named window specifications (i.e., the content of over_clauses) for analytic functions. It allows the association of identifiers (i.e., a window_name) with a specification. By referencing the identifier in the over_clause it is possible to use the same specification several times in a single statement. This shortens the SQL query and increases its readability. Additionally, it is possible to combine named window specifications with each other.