Re: Merging lines with NULLs (with example data)

Harald Fuchs wrote:
> In article <djdp5l$1l4f$1(at)talisker(dot)lacave(dot)net>,
> MaXX <bs139412(at)skynet(dot)be> writes:
>
>
>>How can I "merge" this
>>gday,count_udp,count_tcp
>>'2005-10-20','','2'
>>'2005-10-20','3',''
>>'2005-10-21','','1'
>>'2005-10-21','5',''
>
>
>>into that:
>>gday,count_udp,count_tcp
>>'2005-10-20','3','2'
>>'2005-10-21','5','1'
>
>
>>in a single query???
>
>
> Try something like that:
>
> SELECT to_date (tstamp,'YYYY-MM-DD') AS gday,
> sum(CASE WHEN proto = 'UDP' THEN 1 ELSE 0 END) AS count_udp,
> sum(CASE WHEN proto = 'TCP' THEN 1 ELSE 0 END) AS count_tcp
> FROM test
> WHERE tstamp >= now() - INTERVAL '$days DAYS'
> AND dst_port = $port
> GROUP BY gday
> ORDER BY gday
>

Or, via a subquery:

select distinct to_date(tstamp,'YYYY-MM-DD') as gday,
( select count(id) from test t1 where proto='UDP' and
to_date(t1.tstamp,'YYYY-MM-DD') = to_date(test.tstamp,'YYYY-MM-DD') ) as
count_udp,
( select count(id) from test t1 where proto='TCP' and
to_date(t1.tstamp,'YYYY-MM-DD') = to_date(test.tstamp,'YYYY-MM-DD') ) as
count_tcp
from test
where tstamp >= (now() - interval '6 days' )
and dst_port = 2290
order by gday;

Harald's solution is better for your particular case and will almost
certainly be faster, but subqueries are good to know how to do. :)

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