sql - SQL：连接顺序整数值

Question

我有一个这样的专栏：

ID
--------
1
2
3
4
5
7
10

我想得到以下结果集：

ID
--------
1-5
7
10

有没有办法仅使用（Oracle）SQL 来实现这一点？

Answer 1

是的：

select (case when min(id) < max(id)
             then cast(min(id) as varchar2(255)) || '-' || cast(max(id) as varchar2(255))
             else cast(min(id) as varchar2(255))
        end)
from (select id, id - rownum as grp
      from t
      order by id
     ) t
group by grp
order by min(id);

这是一个演示它的 SQL Fiddle。

查询背后的想法是rownum从一个数字序列中减去一个常数。您可以使用常量进行分组。

Answer 2

自我加入是必要的......我认为这会奏效

Select a.id, b.id
From table a   -- to get beginning of each range
  Join table b -- to get end of each range
    On b.id >= a.Id -- guarantees that b is after a
       And Not exists (Select * From table m  -- this guarantees all values between 
                       where id Between a.id+1 and b.id
                           And Not exists(Select * From table 
                                          Where id = m.id-1))
       And Not exists (Select * From table  -- this guarantees that table a is start 
                       Where id = a.id -1)
       And Not exists (Select * From table  -- this guarantees that table b is end
                       Where id = b.id + 1)