ROW_NUMBER() OVER (PARTITION

Question

hi, can anyone explain, especially this part
ROW_NUMBER() OVER (PARTITION BY A.USER_ID ORDER BY A.TNP_TRACK_ID DESC) RN
Thanks
newbie
SELECT A.TNP_TRACK_ID, A.USER_ID, NVL(A.DELETED,0) DELETED, A.CREATE_TIME, A.DELETE_TIME, B.PRODUCT_CODE, C.LOGIN_NAME,
ROW_NUMBER() OVER (PARTITION BY A.USER_ID ORDER BY A.TNP_TRACK_ID DESC) RN
FROM MISPNA.TNP_TRACKABLE_' || TO_CHAR(p_reporting_month, 'YYYYMM') || ' A
JOIN TMP_VRZ_LATEST_SOC B ON A.TNP_TRACK_ID = B.TRACK_ID
JOIN MISPNA.TN_LOGIN C ON A.USER_ID = C.USER_ID
WHERE A.DELETED<>1

Answer 1

Hi,
949523 wrote:
thank you very much, the whole original script is
SELECT TNP_TRACK_ID, USER_ID, DELETED, CREATE_TIME, DELETE_TIME, PRODUCT_CODE, LOGIN_NAME
FROM (
SELECT A.TNP_TRACK_ID, A.USER_ID, NVL(A.DELETED,0) DELETED, A.CREATE_TIME, A.DELETE_TIME, B.PRODUCT_CODE, C.LOGIN_NAME,
ROW_NUMBER() OVER (PARTITION BY A.USER_ID ORDER BY A.TNP_TRACK_ID DESC) RN
FROM MISPNA.TNP_TRACKABLE_' || TO_CHAR(p_reporting_month, 'YYYYMM') || ' A
JOIN TMP_VRZ_LATEST_SOC B ON A.TNP_TRACK_ID = B.TRACK_ID
JOIN MISPNA.TN_LOGIN C ON A.USER_ID = C.USER_ID
WHERE A.DELETED <>1
WHERE RN != 1';I assume the single-quote near the end is just an editing typo.
>
so seems like with specified user_id, it will pick greatest tnp_track_id ? ( as it asks RN=1)That's what it would be doing if the last line read
WHERE  rn = 1; for each user_id, that query (with = on the last line) would display all the SELECTed values from the row with the greatest tnp_track_id.
Since you're using != , however, then it's doing just the opposite; it's displaying all rows except the row with the greatest tnp_track_id.
The sub-query is necessary here. All analytic functions, including ROW_NUMBER, are evaluated after the WHERE clause has been applied. To use the results of an analytic function in a WHERE clause, you have to compute the function in a sub-query first.
Edited by: Frank Kulash on Jan 7, 2013 8:08 PM
Just noticed you're saying "WHERE RN != 1" ( not equals)