Inventory by LocationId (were locations are hierarchical)

Hi,

I have a problem with an inventory system I'm designing.  It is an inventory system by LocationId.   The problem I have is that the locations are hierarchical.   By hierarchical I mean that a given location might belong to a next location.

For example given the following (simplified) schema of 3 tables (Locations, Articles and Inventory)

CREATE  TABLE Locations (

LocationId                 INTEGER NOT NULL,

ParentLocationId           INTEGER NULL,

CONSTRAINT w_Ub_LLAVE PRIMARY KEY (LocationId)

)

GO

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (1,NULL);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (2,NULL);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (3,NULL);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (4,1);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (5,4);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (6,4);

INSERT INTO Locations (LocationId,ParentLocationId) VALUES (7,5);

CREATE TABLE Articles  (

ItemId                     INTEGER NOT NULL,

Description                VARCHAR(50),

CONSTRAINT ArticlePK PRIMARY KEY (ItemId)

)

GO

INSERT INTO Articles (ItemId,Description)  VALUES (100,'BREAD');

CREATE TABLE Inventory (

LocationId                 INTEGER NOT NULL,

ItemId                     INTEGER NOT NULL,

Qty                        DECIMAL(14,4) NULL,

CONSTRAINT InventoryPK PRIMARY KEY (LocationId,ItemId)

)

GO

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (1,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (2,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (3,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (4,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (5,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (6,100,5);

INSERT INTO Inventory (LocationId,ItemId,Qty) VALUES (7,100,5);

I would like to list the contents by locationId.

For example, if I list LocationId=1 I should get

5 (in LocationId = 1) +

5 (in LocationId = 4 which belongs to 1) +

5 (in LocationId=5 which belongs to 4 which belongs to 1) +

5 (in LocationId=6 which belongs to 4 which belongs to 1) +

5 (in LocationId=7 which belongs to 5 which belongs to 4 which belongs to 1)

= 25

If I list LocationId=7 I would only get 5 (those in locationId=7)

If I list LocationId=5 I would bet 10 (those in LocationId=5 and those in LocationId=7).

Hopefully I was able to explain myself.   Does anybody know how this could be done?

Thanks,

Edgard