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.
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. :(
Dinesh Kumar
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
Just add WHERE val > 0:
ReplyDeleteSELECT 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;
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.
DeleteYou can also use MIN(CASE WHEN val = 0 THEN NULL ELSE val END)
ReplyDeleteThank 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.
DeleteI 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.
DeleteThe following should work as well. MIN(NULLIF(val,0))
ReplyDeleteThanks 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.
DeleteSame anonymous poster. COALESCE(MIN(NULLIF(val,0)),0)
DeleteAh. Yes this one. Thank you very much.
DeletePostgreSQL 9.4: coalesce(min(val) filter (where val > 0), 0)
ReplyDeleteExcellent, nice enhancement.
Delete