From: Peter Brawley Date: April 11 2005 2:56pm Subject: Re: Display 1st row of every group? List-Archive: http://lists.mysql.com/mysql/182441 Message-Id: <425A9020.8010608@earthlink.net> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=======AVGMAIL-425A90200730=======" --=======AVGMAIL-425A90200730======= Content-Type: multipart/alternative; boundary=------------060507050104030501080804 --------------060507050104030501080804 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Thanks to Rhino & Dan for the corrections, HAVING in that query makes it return only id values for which there is one row, and the header is wrong since "first row of every group" doesn't mean anything without explicit ordering. PB ----- Dan Bolser wrote: >On Mon, 11 Apr 2005, Rhino wrote: > > > >>----- Original Message ----- >>From: "Dan Bolser" >>To: >>Sent: Monday, April 11, 2005 5:58 AM >>Subject: Display 1st row of every group? >> >> >> >> >>>I read with great interest this >>> >>>http://www.artfulsoftware.com/queries.php#4 >>> >>>Display 1st row of every group >>> >>>SELECT id >>>FROM tbl >>>GROUP BY id >>>HAVING count(*) = 1; >>> >>> >>> >>Despite what the heading says for that query, it is NOT going to return the >>first row of every group. In fact, it is going to return only groups that >>contain one row. For example, given this data: >> >>ID >>-- >>5 >>5 >>5 >>6 >>7 >>7 >>8 >>8 >>8 >>9 >> >>That query will return return this: >> >>id >>-- >>6 >>9 >> >>In other words, it is returning only groups where there is a single ID with >>that value. Note also that it is returning ONLY an ID, not the ID plus the >>rest of the row. Their description of what the query does is just plain >>wrong. >> >> > >Delicious second opinion! > >Thanks for the reply - if you see my second post you see I fixed my >problem. > >Cheers, >Dan. > > > > --------------060507050104030501080804 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Thanks to Rhino & Dan for the corrections, HAVING in that query makes it return only id values for which there is one row, and the header is wrong since "first row of every group" doesn't mean anything without explicit ordering.

PB

-----

Dan Bolser wrote: 
On Mon, 11 Apr 2005, Rhino wrote:

  
----- Original Message ----- 
From: "Dan Bolser" <dmb@stripped>
To: <mysql@stripped>
Sent: Monday, April 11, 2005 5:58 AM
Subject: Display 1st row of every group?


    
I read with great interest this

http://www.artfulsoftware.com/queries.php#4

Display 1st row of every group

SELECT id
FROM tbl
GROUP BY id
HAVING count(*) = 1;

      
Despite what the heading says for that query, it is NOT going to return the
first row of every group. In fact, it is going to return only groups that
contain one row. For example, given this data:

ID
--
5
5
5
6
7
7
8
8
8
9

That query will return return this:

id
--
6
9

In other words, it is returning only groups where there is a single ID with
that value. Note also that it is returning ONLY an ID, not the ID plus the
rest of the row. Their description of what the query does is just plain
wrong.
    

Delicious second opinion!

Thanks for the reply - if you see my second post you see I fixed my
problem.

Cheers,
Dan.
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