本题中需要注意两个点：去重复值用distinct ，逆序排序用order by 列名 desc; 语法：select distinct salary from salaries order by salary desc; 补充：拓展group by 和order by 1、group by 是分组分类，后面常用having+条件，格式：group by 分类标准 having 筛选条件；例如 group by emp_no having t>15; 2、order by 是排序，默认为升序。其中升序为asc,降序为desc;格式：order by 分类标准；例如order by key_id desc;