Two other commonly-used methods:
SELECT jNMBR, sNMBR
FROM #myTable
WHERE cDate IS NOT NULL
GROUP BY jNMBR, sNMBR
SELECT jNMBR, sNMBR
FROM (
SELECT jNMBR, sNMBR, rn = ROW_NUMBER() OVER(PARTITION BY jNMBR, sNMBR ORDER BY (SELECT NULL))
FROM #myTable
WHERE cDate IS NOT NULL
) d
WHERE rn = 1
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden