Let's say I have an array of integers
1 6 6 3 3 8 4 4
It will be always of the form n*(pairs of number) + 2 (unique numbers)
.
Is there an efficient way of keeping only the 2 uniques values (i.e. the 2 with single occurence)?
Here, I would like to get 1 and 8.
So far is what I have:
SELECT node_id
FROM
( SELECT node_id, COUNT(*)
FROM unnest(array[1, 6, 6 , 3, 3 , 8 , 4 ,4]) AS node_id
GROUP BY node_id
) foo
ORDER BY count LIMIT 2;
You are very close, I think:
SELECT node_id
FROM (SELECT node_id, COUNT(*)
FROM unnest(array[1, 6, 6 , 3, 3 , 8 , 4 ,4]) AS node_id
GROUP BY node_id
HAVING count(*) = 1
) foo ;
You can group these back into an array, if you like, using array_agg()
.