Hi Hugo,

Writing a question to demonstrate the equivalence of SQL expressions is very brave, so well done for that. Small point: in the explanation you say, "the only way to rewrite the query is to reverse the table order", but this code expresses the same SQL semantic I think:

SELECT

e.Name,

c.Name,

o.OrderDate

FROM dbo.Employees AS e

LEFT JOIN

(

dbo.Orders AS o

JOIN dbo.Customers AS c ON

c.CustomerID = o.CustomerID

) ON

e.EmployeeID = o.CustomerID

AND o.OrderDate > DATEADD(MONTH, -4, CURRENT_TIMESTAMP)

WHERE

e.Position = 'SalesRep'

Personally I find this layout easier to read than 'nested' ON clauses.