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How to get non zero min value from MIN(0, 1, 2)

Hi,

Today, i have faced an interesting problem like below.

I want to get MIN(UNNEST(ARRAY[0, 1, 2, ....]))  as non-zero small element. In this case, it's 1.

Below is my problem description.

postgres=# SELECT SUM(val), MAX(val), MIN(val)
FROM
(
SELECT UNNEST(ARRAY[1, 2, 3]) val
UNION ALL
--Appending some dummy rows, for getting what i would like to expect.
SELECT UNNEST(ARRAY[0, 0, 0]) val
) AS FOO;
 sum | max | min
-----+-----+-----
   6 |  3  | 0
(1 row)

As you see, i can able to identify the sum, max without any problem. But when it comes to "min", i am getting the value as 0. But, I want the minimum as 1 as per my requirement. I can able to get the min, max, sum from the first array it self. But, my implementation doesn't allow this. :(

I have tried it in so many ways, and finally found the following solution. I believe, there will be some better ways also, but just wanted to keep a note on this.

postgres=# SELECT SUM(val), MAX(val), 
COALESCE((SELECT * FROM UNNEST(array_agg(val)) WHERE unnest!=0 ORDER BY unnest ASC LIMIT 1), 0) AS min
postgres-# FROM
postgres-# (
postgres(# SELECT UNNEST(ARRAY[1, 2, 3]) val
postgres(# UNION ALL
postgres(# SELECT UNNEST(ARRAY[0, 0, 0]) val
postgres(# ) AS FOO;
 sum | max | min 
-----+-----+-----
   6 |   3 |   1

(1 row)

Hope it helps to someone.


Dinesh Kumar
Labels:

Comments

  1. Bård GrønbechMarch 11, 2014 at 5:17 PM

    Just add WHERE val > 0:

    SELECT SUM(val), MAX(val), MIN(val)
    FROM
    (
    SELECT UNNEST(ARRAY[1, 2, 3]) val
    UNION ALL
    SELECT UNNEST(ARRAY[0, 0, 0]) val
    ) AS FOO
    WHERE val > 0;

    ReplyDelete
    Replies
    1. Dinesh KumarMarch 11, 2014 at 6:34 PM

      Thank you for the answer. Yes, it's the way we can also do. But in the case of the first array , if it's like ARRAY[0, 0, 0] then i don't get any rows. I could post this along with my full requirement. I am really sorry for the partial details.

      Delete
  2. Paul MooreMarch 11, 2014 at 5:26 PM

    You can also use MIN(CASE WHEN val = 0 THEN NULL ELSE val END)

    ReplyDelete
    Replies
    1. Dinesh KumarMarch 11, 2014 at 6:38 PM

      Thank you very much paul. Yes, it defiantly do the same thing. In the case of 1st ARRAY[0, 0, 0] i will get the min as null, where i was expecting to give 0. I am really sorry to post this blog with partial details. I will try to give full details, when i do next time.

      Delete
    2. AnonymousMarch 13, 2014 at 1:00 PM

      I like the 9.4 filter feature otherwise this I like best combined with a coalesce to provide your zero if no non-zero values are present. This is explicit about not evaluating zero while the nullif is maybe shorter but, to me at least, a very non-typical use of that function.

      Delete
  3. AnonymousMarch 11, 2014 at 5:52 PM

    The following should work as well. MIN(NULLIF(val,0))

    ReplyDelete
    Replies
    1. Dinesh KumarMarch 11, 2014 at 6:40 PM

      Thanks for your inputs. i believe this don't work with ARRAY[0, 0, 0]. I am really really sorry to post blog with partial details. Anyhow, thank you very much for your time.

      Delete
    2. AnonymousMarch 11, 2014 at 9:04 PM

      Same anonymous poster. COALESCE(MIN(NULLIF(val,0)),0)

      Delete
    3. Dinesh KumarMarch 11, 2014 at 10:54 PM

      Ah. Yes this one. Thank you very much.

      Delete
  4. AnonymousMarch 11, 2014 at 11:31 PM

    PostgreSQL 9.4: coalesce(min(val) filter (where val > 0), 0)

    ReplyDelete

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