Re: Fetching rows with a specific range

On Dec 22, 2012, at 10:18 AM, Aaron Rosenzweig wrote:

> Hi WOrriors,
> 
> The "SQLHelpers" allow you to randomly pull a handful of records out  
> of a result set. It is up to you to look at them and be sure they are  
> deterministic. I remember the Oracle one that came with wonder was not  
> deterministic but I was not allowed to give back the fix to the  
> community when I worked at clinworX.
> 
> It's not so hard. Spend a few days learning about the nuances of your  
> Database and either fix the Wonder SQL helper or make a new one….


It depends. If you're stuck on Sybase you're boned. Millions of rows and no way to use a batching display group… nice. Real nice.


> or  
> at least confirm. I did confirm the Frontbase one is spot on correct.
> 
> WOnder has sql helpers for most databases.
> 
> See "ERXEOControlUtilities.objectsInRange()" methods. They internally  
> use the sql helpers to do their magic.
> 
> Also see the "ERXBatchingDisplayGroup" as it, too, uses the sql helpers.
> 
> Of course, for simple "first 10" results just use an ordered fetchspec  
> with a fetch limit. But for random grabs, the sql helper does it.
> 
> Cheers,
> -- Aaron
> 
> On Dec 20, 2012, at 3:21 PM, Kieran Kelleher wrote:
> 
>> Hi Ryan,
>> 
>> To get FetchSpec fetchLimit to generate SQL that limits the number  
>> of rows returned from the database you need to have three conditions  
>> (IIRC):
>> 
>> (1) You must use ERXFetchSpecification subclass
>> (2) Your database PlugIn must support it (MySQL does, PostgreSQL  
>> does, not sure about the others)
>> (3) promptsAfterFetchLimit should be false, which is its default  
>> anyway
>> 
>> Also, ERXFetchSpecification supported a fetchRange which is a  
>> similar feature that generates the correct LIMIT statement in MySQL  
>> for example - I don't know if any other db Plugins support fetchRange.
>> 
>> HTH,
>> 
>> Kieran
>> 
>> On Dec 19, 2012, at 9:16 AM, Maik Musall <[email protected]> wrote:
>> 
>>> Hi Ryan,
>>> 
>>> have you tried
>>> 
>>> EOFetchSpecification fspec = ...
>>> fspec.setFetchLimit( 10 );
>>> 
>>> using an EOSortOrdering? That should let the database pre-sort the  
>>> result and stop after 10 rows returned.
>>> 
>>> Maik
>>> 
>>> 
>>> 
>>> Am 19.12.2012 um 14:38 schrieb Y. Dong  
>>> <[email protected]>:
>>> 
>>>> Hi there,
>>>> 
>>>> I would do something like SELECT * FROM  ( SELECT * FROM Articles  
>>>> ORDER BY createdTime) WHERE ROWNUM<=10;
>>>> 
>>>> Semantically it means please give me the oldest 10 articles by  
>>>> createdTime. Any idea how to express this in terms of webobjects.  
>>>> ERXFetchSpecification alone doesn't seem adequate.
>>>> 
>>>> Thanks
>>>> 
>>>> Ryan
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> 
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