What is the ratio of author with affiliation and without affiliation?
with affiliation refers to Affiliation is not Null; without affiliation refers to Affiliation IS NULL; Ration = Count(Id(Affiliation is NOT NULL)) : Count (Id (Affiliation IS NULL))
SELECT CAST(SUM(CASE WHEN Affiliation IS NULL THEN 1 ELSE 0 END) AS REAL) / COUNT(*) FROM Author
database name:db_id authors
Author table Author Cols: Id dtype integer, Name dtype text, Affiliation dtype text, 
Conference table Conference Cols: Id dtype integer, ShortName dtype text, FullName dtype text, HomePage dtype text, 
Journal table Journal Cols: Id dtype integer, ShortName dtype text, FullName dtype text, HomePage dtype text, 
Paper table Paper Cols: Id dtype integer, Title dtype text, Year dtype integer, ConferenceId dtype integer, JournalId dtype integer, Keyword dtype text, 
PaperAuthor table PaperAuthor Cols: PaperId dtype integer, AuthorId dtype integer, Name dtype text, Affiliation dtype text, 
