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Timeslice/ reporting 'empty' bins as zero

Hello,
first: my SQL and vertica knowledge is quite limited.
I have a table that contains data samples with a timestamp, and I am counting the number of data items e.g. on a 5min interval using the time_slice function like this:

select time_slice(to_timestamp(timestamp_utc_s),$interval), 'my_table=' || count(*) from dataset.my_table group by 1 order by 1 desc;

Sample Result:
2022-04-11 11:10:00 | my_table=1000
2022-04-11 11:05:00 | my_table=1000
2022-04-11 11:00:00 | my_table=196
2022-04-11 09:50:00 | my_table=588
2022-04-11 09:45:00 | my_table=1000
2022-04-11 09:40:00 | my_table=1000
2022-04-11 09:35:00 | my_table=1000

This is working nicely, however when I have intervals without samples at all, those bins are not reported with a counter of 0, but they are omitted.
Like in the example above between 09:50 and 11:00 .

I am looking for some magic that would make these bins appear with a count of zero :-)

Any hints?

Comments

  • marcothesanemarcothesane Administrator

    Try creating a helper table out of dataset.my_table and left join with that.

    Your query does not seem to be syntactically correct, so I won't bother with it, but just continue from your result table as your intermediate result. Put your original query instead of my UNION ALL SELECT expression into my first CTE called intermediate_result .

    WITH                                                                                                                                                        
    -- your sample result as a Common Table Expression (CTE) ....
    intermediate_result(ts,rs) AS (
              SELECT TIMESTAMP '2022-04-11 11:10:00','my_table=1000'
    UNION ALL SELECT TIMESTAMP '2022-04-11 11:05:00','my_table=1000'
    UNION ALL SELECT TIMESTAMP '2022-04-11 11:00:00','my_table=196'
    UNION ALL SELECT TIMESTAMP '2022-04-11 09:50:00','my_table=588'
    UNION ALL SELECT TIMESTAMP '2022-04-11 09:45:00','my_table=1000'
    UNION ALL SELECT TIMESTAMP '2022-04-11 09:40:00','my_table=1000'
    UNION ALL SELECT TIMESTAMP '2022-04-11 09:35:00','my_table=1000'
    )
    ,
    -- next CTE ..
    ts(ts) AS (
      SELECT
        tms AS ts
      FROM intermediate_result
      TIMESERIES tms AS '5 MINUTES' OVER(ORDER BY ts)
    )
    SELECT
      ts.ts
    , NVL(rs,'my_table=0') AS rs
    FROM ts
    LEFT JOIN intermediate_result USING(ts)
    ORDER BY 1;
    -- out          ts          |      rs       
    -- out ---------------------+---------------
    -- out  2022-04-11 09:35:00 | my_table=1000
    -- out  2022-04-11 09:40:00 | my_table=1000
    -- out  2022-04-11 09:45:00 | my_table=1000
    -- out  2022-04-11 09:50:00 | my_table=588
    -- out  2022-04-11 09:55:00 | my_table=0
    -- out  2022-04-11 10:00:00 | my_table=0
    -- out  2022-04-11 10:05:00 | my_table=0
    -- out  2022-04-11 10:10:00 | my_table=0
    -- out  2022-04-11 10:15:00 | my_table=0
    -- out  2022-04-11 10:20:00 | my_table=0
    -- out  2022-04-11 10:25:00 | my_table=0
    -- out  2022-04-11 10:30:00 | my_table=0
    -- out  2022-04-11 10:35:00 | my_table=0
    -- out  2022-04-11 10:40:00 | my_table=0
    -- out  2022-04-11 10:45:00 | my_table=0
    -- out  2022-04-11 10:50:00 | my_table=0
    -- out  2022-04-11 10:55:00 | my_table=0
    -- out  2022-04-11 11:00:00 | my_table=196
    -- out  2022-04-11 11:05:00 | my_table=1000
    -- out  2022-04-11 11:10:00 | my_table=1000
    
  • aklaeraklaer Employee

    Thanks very much for the hint with the helper table, I will give that a try!

  • aklaeraklaer Employee

    ok, your hint was great, problem solved :-)

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