二、排序数据

2.1 按单个列排序
>>> select * from trade order by trade_time;

2.2 按多个列排序
>>> select * from trade order by trade_time,book_name;
返回结果先按trade_time排序，再对trade_time相等的数据按book_name排序

2.3 指定排序方向
默认是升序排序ASC，也支持降序排列DESC
>>> select * from trade order by trade_time DESC;

2.4 order by子句和limit子句组合
>>> select * from trade order by trade_time DESC limit 1;
找出最新一笔交易时间的数据。