Oracle Database
Recupero gerarchico con Oracle Database 12C

introduzione

Uso del collegamento CONNECT BY

SELECT E.EMPLOYEE_ID,E.LAST_NAME,E.MANAGER_ID FROM HR.EMPLOYEES E
CONNECT BY PRIOR E.EMPLOYEE_ID = E.MANAGER_ID;

La clausola CONNECT BY per definire la relazione tra dipendenti e manager.

Specificare la direzione della query dall'alto verso il basso

SELECT E.LAST_NAME|| ' reports to ' ||
PRIOR E.LAST_NAME "Walk Top Down"  
FROM HR.EMPLOYEES E
START WITH E.MANAGER_ID IS NULL
CONNECT BY PRIOR E.EMPLOYEE_ID = E.MANAGER_ID;