Nice easy Question, but again it makes me think...
Which of these the the better performs better, and what factors determine that?
SELECT DISTINCT *
FROM (VALUES (1), (2), (3), (1)) AS t1(id)
UNION ALL
SELECT DISTINCT *
FROM (VALUES (4), (5))    AS t2(i

OR THIS

SELECT *
FROM (VALUES (1), (2), (3), (1)) AS t1(id)
UNION
SELECT *
FROM (VALUES (4), (5))    AS t2(id)d)