LEFT JOIN vs Stacked Left Join - sql

Question

I wanted to ask whats the difference between those two queries:
SELECT
Customers.CustomerID, Customers.CustomerName, Orders.OrderID,
OrderDetails.Quantity, Products.ProductName
FROM
Customers
LEFT JOIN
(Orders
LEFT JOIN
(OrderDetails
LEFT JOIN
Products ON Products.ProductID = OrderDetails.ProductID
) ON OrderDetails.OrderID = Orders.OrderID
) ON Customers.CustomerID = Orders.CustomerID
GROUP BY
Customers.CustomerName;
Vs
SELECT
Customers.CustomerID, Customers.CustomerName, Orders.OrderID,
OrderDetails.Quantity, Products.ProductName
FROM
Customers
LEFT JOIN
Orders ON Orders.CustomerID = Customers.CustomerID
LEFT JOIN
OrderDetails ON OrderDetails.OrderID = Orders.OrderID
LEFT JOIN
Products ON Products.ProductID = OrderDetails.ProductID
GROUP BY
Customers.CustomerName;
Tested here
https://www.w3schools.com/sql/trysql.asp?filename=trysql_select_join
From what I can see one selects the first of multiple entries, one selects the last of multiple entries, but is that all?
From my point of view the not nested LEFT Join is way easier to read and to understand. Is there any downside of using it?

Answer 1

Your problem is the incorrect use of GROUP BY. The only unaggregated columns in the SELECT should be in the GROUP BY.
The rest of this answer addresses the point about joins.
Your second query is interpreted as:
FROM (((Customers c LEFT JOIN
Orders o
ON o.CustomerID = c.CustomerID
) LEFT JOIN
OrderDetails
ON od.OrderID = o.OrderID
) LEFT JOIN
Products p
ON p.ProductID = od.ProductID
The parentheses can affect the interpretation. But what effect? Essentially, you have:
(((c left join o) left join od) left join p)
versus
c left join (o left join (od left join p)))
Both keep all records in c, regardless of matches in the second. In this case, the two versions do the same thing. But for a particular reason -- the on conditions are strictly chained (that is, c to o, o to od, od to p). If p where joined to o instead of od, then subtle differences can occur.
What are the subtle differences? Two things can differ:
Whether columns from a particular table are NULL or have values.
Whether rows get duplicated, due to multiple matches between two tables.
In practice, I don't fine parentheses particularly useful. If I can about JOIN order, I use an explicit subquery or CTE>