Rank function creating duplicate partitions? (two rank 1's for the same key) The below query is outputting two rows. Given that I am partitioning on ref_number and also have ref_number in the where clause, I believe I should only ever get a single row back. 

WITH rank_cte AS (SELECT  ref_number, RANK()
        OVER(
            PARTITION BY
                ref_number
            ORDER BY
                Logged_Date DESC
        ) AS "Rank1"
From my_table )

SELECT * FROM rank_cte
WHERE Rank1= 1 and ref_number = 'abcd'


What is likely to have caused this? SQL Server must think they are similar enough for the where clause to return both rows, but different enough to partition them.
Found the problem, there were ties in the rank ordering, hence why multiple rows are returned with the same rank id.

The solution will be for me to find an ordering key that has unique combinations of partition and order key.