Odd Outer Joining Structure for a View - sql

Question

I am importing a view from an old database as part of a software upgrade and I saw this FROM clause as I was working.
FROM
t_store_master AS STM
RIGHT OUTER JOIN
dbo.t_shipping AS SHP
INNER JOIN
t_hu_master AS HUM
INNER JOIN
t_stored_item AS STO ON HUM.hu_id = STO.hu_id
ON SHP.shipment_id = HUM.reserved_for
AND SHP.location_id = HUM.location_id
INNER JOIN
dbo.t_carrier AS CAR ON SHP.carrier_code = CAR.carrier_code
LEFT OUTER JOIN
dbo.t_order_detail AS ORD
INNER JOIN
dbo.t_order AS ORM ON ORD.order_number = ORM.order_number
INNER JOIN
dbo.t_pick_detail PDL ON ORD.order_number = PDL.order_number
ON STO.type = PDL.pick_id
ON STM.store_id = HUM.control_number_2
It is my understanding that OUTER JOIN requires an ON clause in order to be interpreted properly by the compiler. However, there must be some edge case scenarios I am unaware of because the code above returns good data without throwing any errors.
After some goggling and reading up on MSDN standards for OUTER JOINs, I am still at a loss for what the LEFT OUTER JOIN and RIGHT OUTER JOIN are doing in this query.
I do know that the multiple ON clauses beneath the INNER JOINs are necessary. There seems to be some kind of hidden or implied mapping being done between the ON clauses and the OUTER JOINs. Past that I cannot tell what the purpose of writing a query this way would be.
Could someone shed some insight on how this works and why it would be written this way?

Answer 1

This is allowed. It makes slightly more sense with parentheses:
FROM t_store_master STM RIGHT OUTER JOIN
(dbo.t_shipping SHP INNER JOIN
(t_hu_master HUM INNER JOIN
t_stored_item STO
ON HUM.hu_id = STO.hu_id
)
ON SHP.shipment_id = HUM.reserved_for AND
SHP.location_id = HUM.location_id
) INNER JOIN
(dbo.t_carrier CAR
ON SHP.carrier_code = CAR.carrier_code LEFT OUTER JOIN
((dbo.t_order_detail ORD INNER JOIN
dbo.t_order ORM
ON ORD.order_number = ORM.order_number
) INNER JOIN
dbo.t_pick_detail PDL
ON ORD.order_number = PDL.order_number
)
ON STO.type = PDL.pick_id
)
ON STM.store_id = HUM.control_number_2
That said, I would recommend never writing a query like this and rewriting the query ASAP if it is in production code. At the very least, add the parentheses!
Parentheses are almost never needed in the FROM clause to express JOINs (there is one case where I do happen to use them). Non-interleaved ON clauses are never needed -- or at least, I have never had occasion to use them or think they were the best way to write a query. But, both are allowed.