How Do I Show A Zero In A "Select Count(*) Group By " When No Rows Where Found

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Hi
I have a table like this

id |	park |	visitors |	date
1 |	1 |	20 | 	1/1/2014
2 |	2 |	20 |	1/1/2014
3 |	3 |	15 |	1/1/2014
4 |	4 |	13 |	1/1/2014
5 |	5 |	45 |	1/1/2014
6 |	1 |	20 |	1/1/2014
7 |	2 |	20 |	1/1/2014
8 |	3 |	15 |	1/1/2014
9 |	4 |	13 |	1/1/2014
10 |	5 |	45 |	1/1/2014
11 |	1 |	20 |	1/2/2014
12 |	2 |	20 |	1/2/2014
13 |	3 |	15 |	1/2/2014
14 |	5 |	45 |	1/2/2014

Notice: in 1/2/2014 there are not registered visitors for Park 4
I tried to do a query to show a result like this:

park |	visitors_per_day |	dateCol 
1 | 	40 |	             1/1/2014
2 |	40 |	             1/1/2014
3 |	30 |	             1/1/2014
4 |	26 | 	             1/1/2014
5 |	90 |	             1/1/2014
1 |	20 |	             1/2/2014
2 |	20 |	             1/2/2014
3 |	15 |	             1/2/2014
4 |	0 |	             1/2/2014
5 |	45 |	             1/2/2014

This is my query

select park, count(*) as visitors_per_day, dateCol from oneTable group by park, dateCol order by dateCol, park
Actually, my query does not show the Park 4 in 1/2/2014, see next example

park |  visitors_per_day |  dateCol
1 |     40 |                 1/1/2014
2 | 40 |                 1/1/2014
3 | 30 |                 1/1/2014
4 | 26 |                 1/1/2014
5 | 90 |                 1/1/2014
1 | 20 |                 1/2/2014
2 | 20 |                 1/2/2014
3 | 15 |                 1/2/2014
5 | 45 |                 1/2/2014

Is it possible to show the park 4 with a zero ?
I'm using Netezza (based on postgresql 7)
PS: sorry for my bad english... it's not my mother tongue

Posted 12-Jun-14 10:29am

bcasillas

Updated 13-Jun-14 11:06am

v6

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PIEBALDconsult · Answer 1 · 2014-06-12T12:19:00

Solution 1

Dunno, but with Sql Server you can use ISNULL(COUNT(*),0)

Posted 12-Jun-14 12:19pm

PIEBALDconsult

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bcasillas 13-Jun-14 17:08pm

that just works if the result set, show de Park 4 with a NULL in the column visitors_per_day
the problems is "the day 1/2/2014, does not show the park 4"
thanks anymay

phil.o · Answer 2 · 2014-06-12T12:33:00

Solution 2

In complement of PIEBALD's answer, I found that could maybe be useful to you:
SO: What is the PostgreSQL equivalent for ISNULL()[^]

Unfortunately, I don't know anything, or almost, about PostgreSQL.
Good luck.

Posted 12-Jun-14 12:33pm

phil.o