SELECT avg(floors) ,  max(floors) ,  min(floors) FROM building
What are the average, maximum, and minimum number of floors for all buildings?
[Schema (values) (types)]: | protein_institute |  building : building_id (text) , name (text) , street_address (text) , years_as_tallest (text) , height_feet (text) , floors (number) | Institution : institution_id (text) , institution (text) , location (text) , founded (text) , type (text) , enrollment (number) , team (number) , primary_conference (text) , building_id (text) | protein : common_name (text) , protein_name (text) , divergence_from_human_lineage (text) , accession_number (text) , sequence_length (text) , sequence_identity_to_human_protein (number) , institution_id (number);