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Posted to user@cayenne.apache.org by Jack O'Connor <jo...@bristol.ac.uk> on 2007/07/23 12:49:56 UTC

counting rows

A question about efficiency: Counting the number of rows in a table.

Currently, I run a select query, then iterate through the rows, 
incrementing a counter. This takes too long. Is there a way to use the 
SQL command:
SELECT count(*) FROM <table>

Or something similar, that quickly returns the number of rows from a 
select query?

Thanks
Jack

Re: counting rows

Posted by Andrus Adamchik <an...@objectstyle.org>.
And another 3.0 plug :-)

Admittedly getting results of scalar queries as Maps can be  
confusing, as (a) you have to unwrap them and (b) it is not always  
clear what the map keys are. So we are experimenting with a different  
presentation of the results. There's more work to be done on that,  
but you can do this already:

  String ejbql = "select count(p) from Painting p";
  EJBQLQuery query = new EJBQLQuery(ejbql);

  Number count = (Number) DataObjectUtils.objectForQuery(context,  
query);

Andrus


On Jul 23, 2007, at 4:57 PM, Aristedes Maniatis wrote:

>
> On 23/07/2007, at 8:49 PM, Jack O'Connor wrote:
>
>> Or something similar, that quickly returns the number of rows from  
>> a select query?
>
> If you don't need the actual records, but just the count, then you  
> can use one of the several mechanisms to do this. Here's one:
>
> http://cayenne.apache.org/doc/customizing-queries.html
>
>
> Ari Maniatis
>
>
> -------------------------->
> Aristedes Maniatis
> phone +61 2 9660 9700
> PGP fingerprint 08 57 20 4B 80 69 59 E2  A9 BF 2D 48 C2 20 0C C8
>
>

Re: counting rows

Posted by Aristedes Maniatis <ar...@maniatis.org>.
On 23/07/2007, at 8:49 PM, Jack O'Connor wrote:

> Or something similar, that quickly returns the number of rows from  
> a select query?

If you don't need the actual records, but just the count, then you  
can use one of the several mechanisms to do this. Here's one:

http://cayenne.apache.org/doc/customizing-queries.html


Ari Maniatis


-------------------------->
Aristedes Maniatis
phone +61 2 9660 9700
PGP fingerprint 08 57 20 4B 80 69 59 E2  A9 BF 2D 48 C2 20 0C C8

AW: counting rows

Posted by Peter Schröder <Pe...@freenet-ag.de>.
hi jack,

search the list on count query. 

-----Ursprüngliche Nachricht-----
Von: Jack O'Connor [mailto:jo4185@bristol.ac.uk] 
Gesendet: Montag, 23. Juli 2007 12:50
An: user@cayenne.apache.org
Betreff: counting rows

A question about efficiency: Counting the number of rows in a table.

Currently, I run a select query, then iterate through the rows, 
incrementing a counter. This takes too long. Is there a way to use the 
SQL command:
SELECT count(*) FROM <table>

Or something similar, that quickly returns the number of rows from a 
select query?

Thanks
Jack