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?
journal ID of 200 to 300 refers to JournalId BETWEEN 200 AND 300; short name starts with A refers to ShortName LIKE 'A%'; Percentage = Divide (Count(ConferenceId = 0), Count(ConferenceId)) * 100
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%'