SQL Join doesn't match all elements - sql

Question

I was solving this question: How can I randomly do a partial outer join in SQL At the end didnt work because can assign multiple times the same row.
But I have a behavior I can't explain where the query doesn't return the expected number of rows
SQL DEMO
WITH tableA as (
SELECT T.id
FROM ( VALUES (111), (222), (333), (444), (555) ) T(id)
), tableB as (
SELECT *, row_number() over (order by note) as rn
FROM ( VALUES ('a'), ('b'), ('c'), ('d'), ('e'),
('f'), ('g'), ('h'), ('i'), ('j'),
('k'), ('l'), ('m'), ('n'), ('o')
) T(note)
), parameter as (
SELECT 3 as row_limit, (SELECT MAX(rn) FROM tableB) as max_limit
), Nums AS (
SELECT n = ROW_NUMBER() OVER (ORDER BY [object_id])
FROM sys.all_objects
), random_id as (
SELECT tableA.*, T.n, floor(p.max_limit * RAND(convert(varbinary, newid()))) + 1 magic_number
FROM tableA
CROSS JOIN parameter p
CROSS JOIN (SELECT n
FROM Nums
CROSS JOIN parameter p
WHERE n <= p.row_limit ) T
)
-- SELECT * FROM random_id
SELECT R.*, note
FROM random_id R
JOIN tableB
ON R.magic_number = tableB.rn
ORDER BY id
The setup: tableA 5 rows, tableB 15 rows. 3 random tableB rows for each row in tableA. So in total should return 3 * 5 = 15 rows
I create a row_number() from 1 to 15 to match to the magic number
Create the random_id cte to assing three random number to each row of tableA. Here you can see the 15 rows with a random number, also show the problem when assign same value twice
SELECT * FROM random_id;
But the JOIN return a random number of rows. more and less than 15
SELECT R.*, note
FROM random_id R
JOIN tableB
ON R.magic_number = tableB.rn
ORDER BY id
But if I use LEFT JOIN instead always return 15 rows.
Question: If random_id cte always return 15 rows how JOIN return more rows, and how return less if all rn values are in the tableB.
And how LEFT JOIN always return 15 rows.
I just test another query where I include the n value and the JOIN

Answer 1

Unfortunately you would have to persist the rows that are using the magic_number to temporary table or other similar construct.
rextester demo here: http://rextester.com/ICS74177
Unfortunately persisting it to a temporary table does result in a loss of elegance of the answer you were attempting. I have run into the same situation in the past trying to do the same thing and encountered the same bug. It's both somewhat exciting and ultimately disappointing when you run into it for the first time, so congrats on that at least!
I can not explain it any better, so please upvote Paul White's answer here: https://dba.stackexchange.com/a/30348/43889
Reference:
bug with newid() and table expressions (ctes)
newid() In Joined Virtual Table Causes Unintended Cross Apply Behavior - Answer by Paul White