IFNULL

How do I add " IFNULL " to the LEFT JOIN query?  I either want the result
from the database or a 0 instead of the word NULL

Ron

SELECT `store_product_profile`.`reference` , inventory.inventory, 
sold_1.quantity, sold_2.quantity, sold_3.quantity
FROM `store_product_profile`

LEFT JOIN (

SELECT `store_product_inventory_control`.`store_product_profile_reference`
, SUM( `store_product_inventory_control`.`quantity` ) AS inventory
FROM `store_product_inventory_control`
GROUP BY `store_product_inventory_control`.`store_product_profile_reference`
) AS inventory ON `store_product_profile`.`reference` =
`inventory`.`store_product_profile_reference`