sql查询：哪些学生有重复主题？

Question

表结构如下：

student area yearlevel code year sem result
123010  INFO         9 0002 2015   1     77
123011  INFO         9 0002 2015   1     70
123012  INFO         9 0002 2015   1     55
123037  INFO         9 0002 2016   2     49
123037  INFO         9 0002 2017   1   NULL
123010  COMP         9 0007 2016   1     82
123010  ISYS         9 0026 2015   2     82
123011  ISYS         9 0026 2015   2     88
123012  ISYS         9 0026 2015   2     66
123010  COMP         9 0038 2016   2     77
123010  COMP         9 0041 2016   1     45
123010  COMP         9 0041 2017   1   NULL
123010  ISYS         9 0049 2016   1     88

因此，学生101有一个重复的主题000002

Answer 1

使用GROUP BY和HAVING功能：

  SELECT student,subject 
  FROM your_table 
  GROUP BY student,subject 
  HAVING COUNT (*) > 1   

Answer 2

这应该有效：

select Student,subject from table group by student, subject having count(*)>1