hi all:
I have a table with columns(>2) named "query", "pop", "dfk".
what I want is:
when I do some select, if the column "query" in result records have
duplicate value, I only want the record which have the maximum value of
the "pop".
for example, the content of table:
query pop dfk
-----------------------
abc 30 1 --max
foo 20 lk --max
def 16 kj --max
foo 15 fk --discard
abc 10 2 --discard
bar 8 are --max
the result should be:
query pop dfk
-----------------------
abc 30 1
foo 20 lk
def 16 kj
bar 8 are
now, I do it like this(plpgsql)
------------------------------------
declare hq := ''::hstore;
begin
for rc in execute 'select * from test order by pop desc' loop
if not defined(hq, rc.query) then
hq := hq || (rc.query => '1')::hstore;
return next rc;
end if;
end loop;
-----------------------------------
language sql/plpgsql will be ok.
ps: I try to use "group by" or "max" function, because of the
multi-columns(more than 2), I failed.
thanks,
any answer is appreciated.
regards,
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