// 获取数据库中旧的表
NSArray* existsTables = [self sqliteExistsTables];
NSMutableArray* tmpExistsTables = [NSMutableArray array];
        
// 修改表名,添加后缀“_bak”，把旧的表当做备份表
for (NSString* tablename in existsTables) {
    [tmpExistsTables addObject:[NSString stringWithFormat:@"%@_bak", tablename]];
    [self.databaseQueue inDatabase:^(FMDatabase *db) {
    NSString* sql = [NSString stringWithFormat:@"ALTER TABLE %@ RENAME TO %@_bak", tablename, tablename];
        [db executeUpdate:sql];
    }];
}