Question

请建议使用SQL查询来获取

“如果学生在多个科目中得分相同，则学生和相应科目列表中的学生得分相同”

例如

Student Subject Score
John    Science 80
John    Maths   80
John    English 80
John    French  80
Peter   Science 85
Peter   Maths   70
Peter   English 70
Peter   French  70
Mathews French  70

Expected Result :
John    Science
John    Maths
John    English
John    French
Peter   Maths
Peter   English
Peter   French

尝试过 -

select person , subject where person in 
( select person , score , count(score) group by person , score having count(score) > 1 )

但是出现了“彼得科学”，这不是必需的。

请协助。

由于

Answer 1

尝试：

select person , subject 
from table t
  join 
     ( select person , score , count(score) 
       from table
       group by person , score having count(score) > 1 
     ) foo
       on t.person = foo.person
 where t.person = foo.person 
   and t.score = foo.score

您的查询不起作用的原因（除了不包括表格）：您的内部查询是选择符合您条件的学生和分数。但是你的外部询问是为符合标准的所有学生选择所有，这就是为什么要包括“彼得科学”的原因。因此，您需要将外部查询中的结果限制为仅匹配所有条件的结果。

Answer 2

您应该告诉我们您使用的是哪种RDBMS。但这应该适用于所有地方：

select 
    t.*
from <tableName> t
join (
    select
        student, score
    from <tableName>
    group by 
        student, score
    having count(*)>1 
) x
on  t.student=x.student
and t.score=x.score

您的查询中遗漏了FROM <tableName>。

Answer 3

试试这个：

select student, subject
from Person 
where student + cast(score as varchar(20)) in 
(   
    select student + cast(score as varchar(20)) from Person group by student,score having count(score) > 1 
)

Answer 4

您可以像示例一样实现此目标自联接表：

SELECT
  t.Student,
  t.Subject,
  t.Score
FROM Table1 AS t
  JOIN 
    (
        SELECT Student, Score FROM Table1 GROUP BY Student, Score HAVING COUNT(*) > 1
    ) AS t1 ON t.Student = t1.Student AND t.Score = t1.Score

您可以在此处找到测试数据和创建表的完整示例：

http://sqlfiddle.com/#!2/61f02/8

SQL - 使用Join / Having / Subquery查询 - 如何使用

4 个答案: