In how many papers and in what years was the International Conference on Database Theory published?
the International Conference on Database Theory refers to FullName = 'International Conference on Database Theory'; published refers to year ! = 0
SELECT COUNT(T1.Id) AS PAPER, COUNT(DISTINCT T1.Year) AS YEARS FROM Paper AS T1 INNER JOIN Conference AS T2 ON T1.ConferenceId = T2.Id WHERE year != 0 AND T2.FullName = 'International Conference on Database Theory'
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, 
