order by a desc,b desc與order by a,b desc的區別

表爲：

通過下面sql看出 order by 默認是asc 。相當於select * from order_table order by id1 asc

通過下面兩個圖可知，

 select * from order_table order by id1,id2 desc不等於 select * from order_table order by id1 desc,id2 desc.

select * from order_table order by id1,id2 desc等於select * from order_table order by id1 asc,id2 desc

通過上圖和下圖可知，select * from order_table order by id1 desc,id2 desc不等於 select * from order_table order by id2 desc,id1 desc.誰在前優先級高，先排序id1，id1相同的情況下再排序id2