How to select all records from multiple tables in MySQL even if no match in some tables

I have three tables (Stores, Item & StoreInv) and I am trying to do a join that contains all records from Stores & Items even if there are no matching records in StoreInv. Probably easiest to explain by an example:

Store table:

StoreId
-------
Store1
Store2
Store3

Item table:

ItemId
-------
A
B
C

StoreInv table (only contains records for Items with inventory at the store):

ItemId    StoreId    Qty 
-------   -------    ---
A         Store1      6
B         Store1      2
B         Store2      4

Desired output:

StoreId    ItemId   Qty 
-------    ------   ---
Store1     A         6
Store2     A         0 (or null)
Store3     A         0 (or null)
Store1     B         2
Store2     B         4
Store3     B         0 (or null)
Store1     C         0 (or null)
Store2     C         0 (or null)
Store3     C         0 (or null)

What I have tried:

SELECT str.StoreId, itm.ItemId, inv.Qty
FROM Item itm
LEFT JOIN StoreInv inv ON inv.ItemId = itm.ItemId
RIGHT JOIN Stores str on str.StoreId = inv.StoreId

Result (not what I want):

StoreId    ItemId   Qty 
-------    ------   ---
Store1     A         6
Store1     B         2
Store2     B         4
Store3     null      null

>Solution :

You should CROSS JOIN the Stores and Inv table to get all the possible combinations. Then LEFT JOIN the StoreInv table to get the quantities of each.

SELECT str.StoreId, itm.ItemId, IFNULL(inv.Qty, 0) Qty
FROM Item itm
CROSS JOIN Stores str
LEFT JOIN StoreInv inv ON inv.ItemId = itm.ItemId AND inv.StoreID = str.StoreID

DEMO