Oracle：分析函数每次值变化后的小计

Question

我有以下数据（示例中的记录顺序）：

A   B
1   10
1   20
1   30
1   40
2   50
2   65
2   75
1   89
1   100

来自SQL：

with x as (
  select A, B
  from (
    select 1 as A, 10 as B from dual
    union all
    select 1 as A, 20 as B from dual
    union all
    select 1 as A, 30 as B from dual
    union all
    select 1 as A, 40 as B from dual
    union all
    select 2 as A, 50 as B from dual
    union all
    select 2 as A, 65 as B from dual
    union all
    select 2 as A, 75 as B from dual
    union all
    select 1 as A, 89 as B from dual
    union all
    select 1 as A, 100 as B from dual
  ) 
)
select A, B
from X

我想对 A 列中每次值更改的数据进行分组， 我想得到以下结果：

A   MIN(B)  MAX(B) 
1   10      40
2   50      75
1   89      100

如何在 ORACLE 11 中获得这样的结果。我希望有一个简单的实现...

Answer 1

这是一个 gaps and islands 问题，已使用 row_number 解析函数解决

SELECT a,
       MIN(b),
       MAX(b)
FROM (
     SELECT x.*,
            ROW_NUMBER() OVER(
                 ORDER BY b
            ) - ROW_NUMBER() OVER(
                 PARTITION BY a
                 ORDER BY b
            ) AS seq
     FROM x
)
GROUP BY a,
         seq;  

Demo