Campi concatenati che utilizzano Connect by Prior

Question

Avere la tabella seguente my_tabe:

M01 |   1
M01 |   2
M02 |   1

Voglio interrogarlo per ottenere:

M01 |   1,2
M02 |   1

Sono riuscito a avvicinarmi usando la seguente query:

with my_tabe as
(
    select 'M01' as scycle, '1' as sdate from dual union
    select 'M01' as scycle, '2' as sdate from dual union
    select 'M02' as scycle, '1' as sdate from dual
)
SELECT scycle, ltrim(sys_connect_by_path(sdate, ','), ',')
FROM
(
    select scycle, sdate, rownum rn
    from my_tabe
    order by 1 desc
)
START WITH rn = 1
CONNECT BY PRIOR rn = rn - 1

Cedendo:

SCYCLE      |   RES
M02         |   1,2,1
M01         |   1,2

Che è sbagliato. Sembra che io sia vicino, ma temo di non farlo qual è il prossimo passo ...

Qualche consiglio?

Answer 1

Devi limitare il tuo connect by allo stesso scycle valore, e conta anche il numero di corrispondenze e filtra su questo per evitare di vedere risultati intermedi.

with my_tabe as
(
    select 'M01' as scycle, '1' as sdate from dual union
    select 'M01' as scycle, '2' as sdate from dual union
    select 'M02' as scycle, '1' as sdate from dual
)
select scycle, ltrim(sys_connect_by_path(sdate, ','), ',')
from
(
    select distinct sdate,
        scycle,
        count(1) over (partition by scycle) as cnt,
        row_number() over (partition by scycle order by sdate) as rn
    from my_tabe
)
where rn = cnt
start with rn = 1
connect by prior rn + 1 = rn
and prior scycle = scycle
/

SCYCLE LTRIM(SYS_CONNECT_BY_PATH(SDATE,','),',')
------ -----------------------------------------
M01    1,2
M02    1

Se sei su 11g puoi usare il integrato LISTAGG funzione invece:

with my_tabe as
(
    select 'M01' as scycle, '1' as sdate from dual union
    select 'M01' as scycle, '2' as sdate from dual union
    select 'M02' as scycle, '1' as sdate from dual
)
select scycle, listagg (sdate, ',') 
within group (order by sdate) res
from my_tabe
group by scycle
/ 

Vengono mostrati entrambi gli approcci (e gli altri) qui.