[英]How can compare if two consecutive rows are arbitrary in SQL Server?
我有一个 SQL 问题,我无法仅使用 SQL 来解决。
问题是:我有一个有 2 列的表。 一个是Question
(int 列),另一个是Answer
( varchar(1)
),如下所示:
Question Answer
--------+---------
1 | A
2 | A
3 | C
4 | D
5 | D
6 | D
7 | E
8 | A
9 | B
10 | A
11 | A
12 | A
Output 应该是这样的;
Range Answer
-----------+----------
1-2 | A
3-3 | C
4-6 | D
7-7 | E
8-8 | A
9-9 | B
10-12 | A
我只是能够做到这一点,
select question, answer
from table
order by answer, question asc
抱歉,我对 SQL 真的很陌生,所以我不知道如何编写此查询..
这是一个差距和孤岛问题。 您可以使用row_number()
枚举答案的值来处理它。 这和问题之间的区别是不变的——识别岛屿:
select min(question), max(question), answer
from (select t.*, row_number() over (partition by answer order by question) as seqnum
from t
) t
group by (question - seqnum), answer
order by min(question);
这是一个差距和孤岛问题。 这是一种使用行号之间的差异来定义组的方法。
select
concat(min(question), '-', max(question)) range,
answer
from (
select
t.*,
row_number() over(order by question) rn1,
row_number() over(partition by answer order by question) rn2
from mytable t
) t
group by answer, rn1 - rn2
order by min(question)
这种方法的好处是,即使question
的数字有差距,它也能工作。
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