SQL - 根据两列选择最新的唯一值

Question

I have this table called TEST in a DB2 Warehouse table:

    DATETIME                NAME  TYPE ANOMALY  CRE_DATE
0   2018-03-05 14:50:30     TEST    UV  0   2018-03-03 12:48:10.058288
1   2018-03-05 14:51:30     TEST    UV  0   2018-03-03 12:50:38.574614
2   2018-03-05 14:51:30     TEST    UV  0   2018-03-03 12:52:01.705416
3   2018-03-05 14:51:30     TEST    UV  0   2018-03-05 13:45:56.937965

What I want to do is select the latest rows (based on CRE_DATE ) with a distinct value of DATETIME where DATETIME is >= (CURRENT DATE -3 DAYS) and NAME='TEST' . I tried to start with this query but I can't get it to work:

SELECT 
    DISTINCT DATETIME, 
    NAME, 
    TYPE, 
    ANOMALY, 
    CRE_DATE 
FROM 
    ML_ANOMALY_EVALUATION 
WHERE 
    ANOMALY=FALSE AND 
    NAME='TEST' 
ORDER BY 
    CRE_DATE DESC

Answer 1

In DB2, the simplest way is to use row_number() :

SELECT mae.*
FROM (SELECT mae.*,
             ROW_NUMBER() OVER (PARTITION BY datetime ORDER BY CRE_DATE DESC) as seqnum
      FROM ML_ANOMALY_EVALUATION mae
      WHERE ANOMALY = FALSE AND NAME = 'HOG.683KQC206' 
     ) mae
WHERE seqnum = 1
ORDER BY CRE_DATE DESC;