Oracle - Convertir la valeur de lignes dans les gammes

Question

Existe-t-il des techniques qui permettraient une ligne du jeu comme celui-ci

WITH 
base AS 
(
    SELECT 1 N FROM DUAL UNION ALL 
    SELECT 2 N FROM DUAL UNION ALL 
    SELECT 3 N FROM DUAL UNION ALL 

    SELECT 6 N FROM DUAL UNION ALL 
    SELECT 7 N FROM DUAL UNION ALL 

    SELECT 17 N FROM DUAL UNION ALL 
    SELECT 18 N FROM DUAL UNION ALL 
    SELECT 19 N FROM DUAL UNION ALL 

    SELECT 21 N FROM DUAL 
) 
SELECT a.N 
FROM base a 

pour obtenir des résultats

1  3 
6  7 
17 19 
21 21 

Il est en effet une des lignes au fonctionnement des gammes. Je joue dans Oracle Land, et j'apprécierais toutes les suggestions.

Answer 1

je me sens comme cela peut sans doute être améliorée, mais il fonctionne:

WITH base AS (
    SELECT 1 N FROM DUAL UNION ALL 
    SELECT 2 N FROM DUAL UNION ALL 
    SELECT 3 N FROM DUAL UNION ALL 
    SELECT 6 N FROM DUAL UNION ALL 
    SELECT 7 N FROM DUAL UNION ALL 
    SELECT 17 N FROM DUAL UNION ALL 
    SELECT 18 N FROM DUAL UNION ALL 
    SELECT 19 N FROM DUAL UNION ALL 
    SELECT 21 N FROM DUAL 
) 
, lagged AS 
(
    SELECT n, LAG(n) OVER (ORDER BY n) lag_n FROM base 
) 
, groups AS 
(
    SELECT n, row_number() OVER (ORDER BY n) groupnum 
     FROM lagged 
     WHERE lag_n IS NULL OR lag_n < n-1 
) 
, grouped AS 
(
    SELECT n, (SELECT MAX(groupnum) FROM groups 
       WHERE groups.n <= base.n 
      ) groupnum 
     FROM base 
) 
SELECT groupnum, MIN(n), MAX(n) 
    FROM grouped 
    GROUP BY groupnum 
    ORDER BY groupnum 

Answer 2

Une autre façon:

WITH base AS 
(
    SELECT 1 N FROM DUAL UNION ALL 
    SELECT 2 N FROM DUAL UNION ALL 
    SELECT 3 N FROM DUAL UNION ALL 
    SELECT 6 N FROM DUAL UNION ALL 
    SELECT 7 N FROM DUAL UNION ALL 
    SELECT 17 N FROM DUAL UNION ALL 
    SELECT 18 N FROM DUAL UNION ALL 
    SELECT 19 N FROM DUAL UNION ALL 
    SELECT 21 N FROM DUAL 
) 
select min(n), max(n) from 
    (
    select n, connect_by_root n root from base 
    connect by prior n = n-1 
    start with n not in (select n from base b 
         where exists (select 1 from base b1 where b1.n = b.n-1) 
         ) 
) 
    group by root 
    order by root 

Answer 3

Encore une autre façon:

with base as (
    select 1 n from dual union all 
    select 2 n from dual union all 
    select 3 n from dual union all 
    select 6 n from dual union all 
    select 7 n from dual union all 
    select 17 n from dual union all 
    select 18 n from dual union all 
    select 19 n from dual union all 
    select 21 n from dual) 
select a,b 
from (select a 
      ,case when b is not null and a is not null 
        then b 
        else lead(n) over (order by n) 
      end b 
     from (select n 
        ,a 
        ,b 
      from (select n 
         ,case n-1 when lag (n) over (order by n) then null else n end a 
         ,case n+1 when lead (n) over (order by n) then null else n end b 
        from base) 
     where a is not null 
     or b is not null)) 
where a is not null 
order by a