SQL rank/dense_rank and how to query/calculate with the result - sql

Question

So I have a table where it dense_ranks my rows.
Here is the table:
COL1 | COL2 | COL3 | DENSE_RANK |
a | b | c | 1 |
a | s | r | 1 |
a | w | f | 1 |
b | b | c | 2 |
c | f | r | 3 |
c | q | d | 3 |
So now I want to select any rows where the rank was only represented once, so the 2 is all alone, but not the 1 or 3. I want to select all the rows where this occurs, but how do I do that?
Some ideas:
-COUNT DISTINCT (RANK())
-COUNT RANK()
but neither of those are working, any ideas? please and thank you!
happy hacking
actual code:
SELECT events.event_type AS "event",
DENSE_RANK() OVER (ORDER BY bw_user_event.pad_id) as rank
FROM user_event
WHERE (software_events.software_id = '8' OR software_events.software_id = '14')
AND (software_events.event_type = 'install')

Answer 1

WITH Dense_ranked_table as (
-- Your select query that generates the table with dense ranks
)
SELECT DENSE_RANK
FROM Dense_ranked_table
GROUP BY DENSE_RANK
HAVING COUNT(DENSE_RANK) = 1;
I don't have SQL Server to test this. So please let me know whether this works or not.

Answer 2

I would think you can add a COUNT(*) OVER (PARTITION BY XXXXX) where XXXXX is what you include in your dense rank.
Then wrap this in a Common Table Expression and select where your new Count is = 1.
Something like this fiddler:
http://sqlfiddle.com/#!6/ae774/1
Code included here as well:
CREATE TABLE T
(
COL1 CHAR,
COL2 CHAR,
COL3 CHAR
);
INSERT INTO T
VALUES
('a','b','c'),
('a','s','r'),
('a','w','f'),
('b','b','c'),
('c','f','r'),
('c','q','d');
WITH CTE AS (
SELECT COL1 ,
COL2 ,
COL3,
DENSE_RANK() OVER (ORDER BY COL1) AS DR,
COUNT(*) OVER (PARTITION BY COL1) AS C
FROM dbo.T AS t
)
SELECT COL1, COL2, COL3, DR
FROM CTE
WHERE C = 1
Would return just the
b, b, c, 2
row from your test data.