public static void dropAllTables(Database db, boolean ifExists) {
        BookDao.dropTable(db, ifExists);
        ChapterDao.dropTable(db, ifExists);
        SearchHistoryDao.dropTable(db, ifExists);
    }
Drops underlying database table using DAOs.
app/src/main/java/com/zhao/myreader/greendao/gen/DaoMaster.java