PLSQL looping through hierarchy - plsql

Question

I am trying to figure out how loop through a hierarchy, I don't know how to put in PLSQL. What I am trying to achieve: I want to know what department is 10 steps above me in a hierarchy:
Say I have a table with a department and a parent department. I want to perform this kind of operation:
select my_department from table_departments as v_department
FOR counter in 1...9
LOOP
v_department:=
(SELECT parent_department
FROM table_department_hierarchy
WHERE child_department=v_department)
END LOOP as top_department;
I can't figure out the correct syntax, is there a brave soul out there who can help me?

Answer 1

Your method with corrected PL/SQL syntax would be something like:
begin
select my_department into v_department from table_departments;
FOR counter in 1...9
LOOP
SELECT parent_department
INTO v_department
FROM table_department_hierarchy
WHERE child_department=v_department;
END LOOP:
END;
However you could perhaps get it all in one statement something like this:
SELECT parent_department
INTO v_department
FROM
( SELECT parent_department, level as lvl
FROM table_department_hierarchy
CONNECT BY child_department = PRIOR parent_department
START WITH child_department = v_department
)
WHERE lvl = 9;
See Oracle docs on hierarchical queries

Answer 2

This is a large pl/sql procedure that i wrote a long while ago that was meant to traverse a employee/boss reporting tree all the way to the top (CEO). This version was specific to Peoplesoft but it as long as your reading something that has a parent/child relationship in a record it will work on anything.... I have other more dynamic versions of this but this maybe the simplest to decipher. I removed some fluff stuff that you won't care about. Also this particular solution delivers to a table for many different reasons because reporting tools can consume it...
Also it determines levels dynamically so you don't have to know how many levels there are as you would with a connect by solution.
Hope it helps:
CREATE OR REPLACE PROCEDURE DW."SPW_T_RESOURCE_HIERARCHY" (iCommit In Integer Default 1000,
pdBegin In Date Default trunc(Sysdate) - 3,
pdEnd In Date Default trunc(Sysdate) + 1,
vTruncate In Varchar2 Default 'Y' ) Is
------------------------------------------------------
-- DECLARATIONS
------------------------------------------------------
Cursor curDataSource Is
---**********************************----
---****BEGIN CUSTOMIZE THIS BLOCK****----
---**********************************----
Select
Eh.empl_id F_DESCENDANT_ID
,Eh.Super_Empl_Id F_IMMEDIATE_ANCESTOR_ID
From
Employee_Header EH
Where
EH.SUPER_EMPL_ID IS NOT NULL OR EH.TERM_DATE IS NULL;
---**********************************----
---****END CUSTOMIZE THIS BLOCK******----
---**********************************----
dNow Date := Sysdate;
iTotalRows Integer := 0;
iTotalErrors Integer := 0;
---**********************************----
---****BEGIN CUSTOMIZE THIS BLOCK****----
---**********************************----
vDescendentID Varchar2(20);
iDescendentLevel Integer := 1;
iAncestorLevel Integer := 0;
vAncestorID Varchar2(20);
vTmpAncestorID Varchar2(20);
vTmpEmployeeID Varchar2(20);
---**********************************----
---****END CUSTOMIZE THIS BLOCK******----
---**********************************----
------------------------------------------------------
-- END DECLARATIONS
------------------------------------------------------
------------------------------------------------------
-- BEGIN MAIN
------------------------------------------------------
Begin
-- Loop over source records
For recDataSource In curDataSource
Loop
iDescendentLevel := 1;
vAncestorID := recDataSource.f_Immediate_Ancestor_Id;
-- Start Transaction
Begin
while (Trim(vAncestorID) is not null)
loop
Begin
-- Fetch Next Ancestor
Select EH.SUPER_EMPL_ID
Into vTmpAncestorID
From
EMPLOYEE_HEADER EH
Where
EH.EMPL_ID = vAncestorID;
Exception
When Others Then
vTmpAncestorID := null;
End;
If NVL(vTmpAncestorID,'-XYZ-') = NVL(vAncestorID,'-123-') Then
vTmpAncestorID := null;
End If;
vAncestorID := vTmpAncestorID;
iDescendentLevel := iDescendentLevel + 1;
end loop;
-- Insert Resource Base
Insert Into T_RESOURCE_HIERARCHY
(
T_RESOURCE_HIERARCHY.F_HIERARCHY_NAME,
T_RESOURCE_HIERARCHY.F_DESCENDANT_LEVEL,
T_RESOURCE_HIERARCHY.F_DESCENDANT_ID,
T_RESOURCE_HIERARCHY.F_ANCESTOR_LEVEL,
T_RESOURCE_HIERARCHY.F_ANCESTOR_ID
)
Values
(
'Physical Org Chart',
iDescendentLevel,
recDataSource.f_Descendant_Id,
To_Number(Decode(iDescendentLevel,1,2,iDescendentLevel) - 1),
NVL(recDataSource.f_Immediate_Ancestor_Id,'ROOT')
);
-- Insert MySelf Into Resource Base as well for full hierarchy research
Insert Into T_RESOURCE_HIERARCHY
(
T_RESOURCE_HIERARCHY.F_HIERARCHY_NAME,
T_RESOURCE_HIERARCHY.F_DESCENDANT_LEVEL,
T_RESOURCE_HIERARCHY.F_DESCENDANT_ID,
T_RESOURCE_HIERARCHY.F_ANCESTOR_LEVEL,
T_RESOURCE_HIERARCHY.F_ANCESTOR_ID
)
Values
(
'Physical Org Chart',
iDescendentLevel,
recDataSource.f_Descendant_Id,
iDescendentLevel,
NVL(recDataSource.f_Descendant_Id,'ROOT')
);
-- Now Its Time To Climb The Tree
-- For This Employee
vAncestorID := recDataSource.f_Immediate_Ancestor_Id;
iAncestorLevel := iDescendentLevel-1;
vTmpAncestorID := null;
-- Loop over parents
while (Trim(vAncestorID) is not null)
loop
Begin
-- Fetch Next Ancestor
Select EH.SUPER_EMPL_ID
Into vTmpAncestorID
From
EMPLOYEE_HEADER EH
Where
EH.EMPL_ID = vAncestorID;
Exception
When Others Then
vTmpAncestorID := null;
End;
If NVL(vTmpAncestorID,'-XYZ-') = '-XYZ-' Then
vTmpAncestorID := null;
End If;
vAncestorID := vTmpAncestorID;
iAncestorLevel := iAncestorLevel - 1;
If vAncestorID is not null Then
-- Insert Resource Base
Insert Into T_RESOURCE_HIERARCHY
(
T_RESOURCE_HIERARCHY.F_HIERARCHY_NAME,
T_RESOURCE_HIERARCHY.F_DESCENDANT_LEVEL,
T_RESOURCE_HIERARCHY.F_DESCENDANT_ID,
T_RESOURCE_HIERARCHY.F_ANCESTOR_LEVEL,
T_RESOURCE_HIERARCHY.F_ANCESTOR_ID
)
Values
(
'Physical Org Chart',
iDescendentLevel,
recDataSource.f_Descendant_Id,
iAncestorLevel,
vAncestorID
);
End If;
end loop;
-- TRANSACTION EXCEPTION HANDLING
Exception
When Others Then
End;
-- ASSIGN HOW MANY RECORDS PROCESSED
iTotalRows := curDataSource%Rowcount;
-- CONDITIONAL/INCREMENTAL TRANSACTION COMMIT
If Mod(iTotalRows, iCommit) = 0
Then
Commit;
End If;
End Loop;
-- FINAL COMMIT AND MD UPDATE
Commit;
-- MAIN EXCEPTION HANDLING
Exception
When Others Then
Begin
iExceptionCode := Sqlcode;
vExceptionMessage := Sqlerrm;
Raise_application_error(Sqlcode, Sqlerrm);
End;
------------------------------------------------------
-- END MAIN
------------------------------------------------------
End SPW_T_RESOURCE_HIERARCHY;
/

Answer 3

Please, check the following example. Not tested, but believe :)
DECLARE
G_EMPLOYEE_ID NUMBER:=1880;
FUNCTION GET_MANAGER(V_EMPLOYEE_ID NUMBER) RETURN NUMBER IS
V_MANAGER_ID NUMBER;
BEGIN
SELECT ID_MANAGER INTO V_MANAGER_ID FROM EMPLOYEES WHERE EMPLOYEE_ID = V_EMPLOYEE_ID;
RETURN V_MANAGER_ID;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END;
BEGIN
LOOP
DBMS_OUTPUT.PUT_LINE('EMPLOYEE:' || G_EMPLOYEE_ID);
G_EMPLOYEE_ID := GET_MANAGER(G_EMPLOYEE_ID);
DBMS_OUTPUT.PUT_LINE('MANAGER:' || G_EMPLOYEE_ID);
EXIT WHEN G_EMPLOYEE_ID IS NULL;
END LOOP;
END;
Another great option (primary) is CONNECT BY, START WITH