Here's the query with standard group_concat and cast:

SELECT CAST(GROUP_CONCAT(`expScores` ORDER BY `i` SEPARATOR '') AS BINARY) 
AS `expScores` FROM `probes` LEFT JOIN `joins` ON `probes`.`id` = `pid` 
 LEFT JOIN `scores` ON `sid` = `scores`.`id` WHERE (`probes`.`eid` = 
(SELECT id FROM `experiments` WHERE (`experiments`.`file` = ?))) GROUP BY 
`joins`.`pid`

The custom aggregate is a binary concat, group_bconcat which avoids the 
implicit cast in group_concat by concatenating primitive arrays. Works with 
BINARY and ARRAY types.

The alternative is to do the concat in the application code, which perhaps 
I should do. It looks like the ORDER BY capability is hard-coded into the 
parser for group_concat, rather than being a generic option for aggregate 
functions.

On Friday, July 26, 2013 12:34:13 AM UTC-7, Noel Grandin wrote:
>
> Do you have a more complete example of what exactly you are trying to do 
> with your custom aggregate? 
>
> On 2013-07-26 00:34, Brian Craft wrote: 
> > I'm unable to use "order by" with a custom aggregate function. E.g 
> > with group_concat, you can do 
> > 
> > group_concat(`foo` order by `bar`) 
> > 
> > however this throws a syntax error with my aggregate function. 
> > 
>
>

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