Database: authors
Question: In papers with journal IDs from 200 to 300 and with its short name starts with A, what is the percentage of papers with conference ID of 0?
SQL: SELECT CAST(SUM(CASE WHEN T1.ConferenceId = 0 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.ConferenceId) FROM Paper AS T1 INNER JOIN Journal AS T2 ON T1.JournalId = T2.Id WHERE T1.JournalId BETWEEN 200 AND 300 AND T2.ShortName LIKE 'A%'