面试题：删除除了自动编号不同, 其他都相同的学生冗余信息

实现思路

首先对自动编号以外的字段进行分组（也就是筛选出非重复的信息）得到临时表，再对两表进行外联操作，删除副表中自动编号为null的信息（也就是重复信息）

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sql语句

delete student from student left join (select min(st.no) as no from student as st group by stu_no,name,course_cd,course_name,score )as temp on student.no = temp.no where temp.no is null;

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或：delete student from student left join (select min(st.no) as no from student as st group by stu_no,name,course_cd,course_name,score )as temp using(no) where temp.no is null;