Re: Postgresql-query for absolute beginner

----- Original Message -----
From: Meike Börder
To: pgsql-novice(at)postgresql(dot)org
Sent: Monday, August 20, 2012 11:55 AM
Subject: [NOVICE] Postgresql-query for absolute beginner

Hey folks,

as you may have guessed from the title, I'm an absolute beginner using PostgreSQL and I need some help. I have a table with the columns 'country' (text), 'sample site' (text) and 'date' (timestamp with time zone):

country sample site date

AA a1 01.01.2000

AA a1 12.02.1999

AA a2 01.01.2000

BB b1 23.04.1984

BB b2 05.05.2000

BB b3 01.01.2000

CC c1 15.03.1998

CC c1 24.10.2002

CC c2 15.03.1998

What I want to know now is how often the different sampling sites were tested. How do I have to write my query? I tried using something like

Select country, sample site, count (date) from samples

But the result was rubbish. I could Imagine that I have to create a loop for this query (the table has overall more than 1 mio rows) to get a result table with a list of sampling sites and the number of surveys for each of them.

Help would be greatly appreciated!

Yours, Meike

You're assuming that a 'sample site' value is either unique or that the count for a site should include all associated countries.

You may, or may not, be right! :-)

Anyhow, please don't top post.

* Yeah, that wouldn't work if two sample sites on different countries happen to have the same name, but from the sample data nothing made me think so, as all sample site ID begin with the same letter as the associated country
Any way, thanks for pointin that out.

Greetings from up over,
Oliver

Cheers,
Gavin