Come scrivere una sottoquery ricorsiva coinvolta in sqlplus con più tabelle per tracciare i nodi?

Nel tuo esempio semplificato (più o meno ho iniziato a usare i nomi delle tue tabelle reali, ma sono i dati originali) puoi ottenere tutti i percorsi attraverso più switch con:

with rcte (rootsectionnumber, fromsectionnumber, tosectionnumber) as (
  select fromsectionnumber, fromsectionnumber, tosectionnumber
  from switchingdevice
  where normalswitchingdevicestate = 'CLOSED'
  union all
  select r.rootsectionnumber, sd.fromsectionnumber, sd.tosectionnumber
  from rcte r
  join switchingdevice sd on sd.fromsectionnumber = r.tosectionnumber
)
select rootsectionnumber, tosectionnumber from rcte;

ROOTSECTIONNUMBER TOSECTIONNUMBER
----------------- ---------------
               54             105
              105             106
              105             999
              999             700
               54             106
              105             500
               54             999
              105             700
               54             500
               54             700

uno dei quali ha un percorso end-to-end dalla sezione 54 alla 700; e puoi quindi unirlo alla definizione del carico:

with rcte (rootsectionnumber, fromsectionnumber, tosectionnumber) as (
  select fromsectionnumber, fromsectionnumber, tosectionnumber
  from switchingdevice
  where normalswitchingdevicestate = 'CLOSED'
  union all
  select r.rootsectionnumber, sd.fromsectionnumber, sd.tosectionnumber
  from rcte r
  join switchingdevice sd on sd.fromsectionnumber = r.tosectionnumber
)
select ld.loadnumber, t.transformernumber
from loaddefinition ld
join rcte r on r.rootsectionnumber = ld.sectionnumber
join transformer t on t.tosectionnumber = r.tosectionnumber
where ld.loadnumber = 100;

LOADNUMBER TRANSFORMERNUMBER
---------- -----------------
       100              5000

O se devi includere il busnumber nella logica (basata su una breve occhiata alla tua query più ampia...):

with rcte (rootsectionnumber, busnumber, fromsectionnumber, tosectionnumber) as (
  select fromsectionnumber, busnumber, fromsectionnumber, tosectionnumber
  from switchingdevice
  where normalswitchingdevicestate = 'CLOSED'
  union all
  select r.rootsectionnumber, r.busnumber, sd.fromsectionnumber, sd.tosectionnumber
  from rcte r
  join switchingdevice sd on sd.fromsectionnumber = r.tosectionnumber
  and sd.busnumber = r.busnumber
)
select ld.loadnumber, t.transformernumber
from loaddefinition ld
join rcte r on r.rootsectionnumber = ld.sectionnumber
and r.busnumber = ld.busnumber
join transformer t on t.tosectionnumber = r.tosectionnumber
and t.tobusnumber = r.busnumber
where ld.loadnumber = 100;

LOADNUMBER TRANSFORMERNUMBER
---------- -----------------
       100              5000

db<>violino

L'aggiunta delle altre tabelle ovviamente complicherà un po' le cose, ma non è chiaro come siano tutte correlate.