sql - Browse subcolumns, but discard some -

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i have table (or view) in postgresql database , want following: query table , feed function in application subsequent n-tuples of rows query, satisfy condition. can n-tuple listing using cursor, don't know how condition checking on database level.

for example, query returns:

3 2 4 2 0 1 4 6 2

and want triples of numbers. here, be: 

(2,4,2) (4,2,0) (4,6,2)

obviously, cannot discard odd numbers query result. instead using cursor, query returning arrays in similar manner acceptable solution, don't have idea how use them this.

of course, check @ application level, think it'd cleaner on database level. possible?

with window function lead() (as mentioned @wildplasser):

select *  (   select tbl_id, i1        , lead(i)    on (order tbl_id) i2        , lead(i, 2) on (order tbl_id) i3     tbl   ) sub  i1%2 = 0 ,    i2%2 = 0 ,    i3%2 = 0;

there no natural order of rows - assuming want order tbl_id in example.
% .. modulo operator

sql fiddle.


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