Question

有一张表格如下

StudentID    Name  Subject
1            AAA   Computers
2            BBB   Computers
2            BBB   Electronics
3            CCC   Electronics

我想将这些数据加载到两个表中，如下所示 OnlyOneSubject Table

StudentID    Name  Subject
1            AAA   Computers
3            CCC   Electronics

MoreThanOneSubject Table

StudentID    Name  Subject
2            BBB   Computers
2            BBB   Electronics

我的sql如下，不确定如何从以下查询中提取数据。

 SELECT *,row_number() over(partition by Name order by Subject) FROM 
 STUDENTS

Answer 1

第一个......

select *
from table
where StudentID in (select StudentID from table group by StudentID having count(*) = 1)

第二个......

select *
from table
where StudentID in (select StudentID from table group by StudentID having count(*) > 1)

但我真的只使用它来返回结果......不需要划分一个你必须经常更新的表。

Answer 2

你可以使用：

WITH STUDENTS(StudentID,Name,Subject)AS(
   SELECT 1,'AAA','Computers' UNION ALL 
   SELECT 2,'BBB','Computers' UNION ALL 
   SELECT 2,'BBB','Electronics' UNION ALL 
   SELECT 3,'CCC','Electronics'
)
select * from (
   SELECT *,count(0) over(partition by Name) as cnt FROM STUDENTS
) as t where cnt=1  ---or cnt>1 for MoreThanOneSubject

StudentID   Name    Subject cnt
1   AAA Computers   1
3   CCC Electronics 1

分组，只导出一个数据集和多个数据集

2 个答案: