假如我要对以下sql查询语句的查询结果进行排序(两个字段a,b)。

select  a,b,c,d,e  from  table_name;

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1.先按照a升序，再按照b降序

select  a,b,c,d,e  from  table_name  order  by a,b desc;

也可以写为(因为默认升序，可以不写)：

select  a,b,c,d,e  from  table_name  order  by  a asc,b desc;

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2.先按照a升序，再按照b升序

select  a,b,c,d,e  from  table_name  order by a,b;

也可以写为：

select  a,b,c,d,e  from  table_name  order by  a asc,b asc;

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3.先按照a降序，再按照b升序

select  a,b,c,d,e  from  table_name  order by  a desc,b;

也可以写为：

select  a,b,c,d,e  from  table_name  order  by  a desc,b asc;

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4.先按照a降序，再按照b降序

select  a,b,c,d,e  from  table_name  order by  a desc,b desc;

注：都降序必须写两个desc，因为排序不写默认asc。