Gives the average number of chapters in Shakespeare's 1599 work.
1599 work refers to Date = '1599'; average number refers to divide(count(chapters.id), count(works.id))
SELECT CAST(COUNT(T1.id) AS REAL) / COUNT(DISTINCT T2.id) FROM chapters AS T1 INNER JOIN works AS T2 ON T1.work_id = T2.id WHERE T2.Date = '1599'
database name:db_id shakespeare
chapters table chapters Cols: id dtype integer, Act dtype integer, Scene dtype integer, Description dtype text, work id dtype integer, 
characters table characters Cols: id dtype integer, char name dtype text, abbreviation dtype text, Description dtype text, 
paragraphs table paragraphs Cols: id dtype integer, paragraph number dtype integer, Plain Text dtype text, character id dtype integer, chapter id dtype integer, 
works table works Cols: id dtype integer, Title dtype text, Long Title dtype text, character id dtype integer, genre type dtype text, 
