When N'' doesn't equal ''.

ANotEqualsA.sql

WITH Algorithms ([algorithm]) AS (
	SELECT [algorithm]
	FROM (VALUES ('MD2'), ('MD4'), ('MD5'), ('SHA'), ('SHA1'), ('SHA2_256'), ('SHA2_512')) AS t([algorithm])
	)
SELECT [algorithm],
	   t.hashed_varchar,
	   u.hashed_nvarchar,
	   checked_varchar = CHECKSUM('a'),
	   checked_nvarchar = CHECKSUM(N'a')
FROM Algorithms
CROSS APPLY (SELECT HASHBYTES([algorithm], CAST('a' AS varchar(1)))) AS t(hashed_varchar)
CROSS APPLY (SELECT HASHBYTES([algorithm], CAST('a' AS nvarchar(1)))) AS u(hashed_nvarchar);
GO