In "Microsoft SQL Server 2016: Querying Data with Transact-SQL" episode "Combining Results with JOIN Part 3" (towards the end), consider this:
SELECT a.[Name],b.[Name],a.CountryRegionCode FROM Sales.SalesTerritory AS a INNER JOIN Sales.SalesTerritory AS b ON a.CountryRegionCode=b.CountryRegionCode AND a.[Name] <> b.[Name] ORDER BY a.CountryRegionCode;
Don Pezet's WHERE clause was redundant with the explicit INNER JOIN. The required ON clause with INNER JOIN took care of the semantics. It's useful to compare my version with Don's final version (both have merit), but comparing Don's first version to his final version leads students to an unfair conclusion.