Calculate the percentage of account from 'Decin' district for all accounts are opened in 1993.
A2 contains the information about district.
SELECT CAST(SUM(T1.A2 = 'Decin') AS REAL) * 100 / COUNT(account_id) FROM district AS T1 INNER JOIN account AS T2 ON T1.district_id = T2.district_id WHERE STRFTIME('%Y', T2.date) = '1993'