sql语句中order by 多个字段同时排序

一、例如："select * from   tablename   where A order by B"

或写成：   "select * from   tablename   where  C  order by A， B"

二、order by A1 , A2  desc   指的是用A1升序A2降序

 

三、order by A1 asc , A2  desc  指的是用A1升序A2降序

 

四、order by A1 desc , A2  desc  指的是用A1降序A2降序