[Qt-interest] SQL (ODBC) retreiving doubles incorrectly

[Bill King]

On 10/02/2009 10:27 PM, ext Andre Somers wrote:
> Julien Cugnière wrote:
>   
>> 2009/10/2 Andre Somers <andre at familiesomers.nl>
>>   
>>     
>>> use qDebug() << on the variant value returned from the query, I get
>>> QVariant(QString, "E-3") as the result. Retreiving the type of the field
>>> using QSqlRecord::field() and QSqlField::type() returns QVariant::double
>>> though.
>>>     
>>>       
>> You can try using query.setNumericalPrecisionPolicy(QSql::LowPrecisionDouble).
>>
>> If you don't, Qt often returns number as strings in order to preserve
>> the precision of the database, which can be greater than that of a
>> double. AFAIK, the exact format of the string is database-dependant,
>> and there's no guarantee it can be parsed by QString::toDouble.
>>
>>
>>   
>>     
> Thanks for the tip, I had not looked into this option before. 
> Unfortunately, it makes things worse. Instead of an QVariant(QString, 
> "E-3") on my debug, I now get an QVariant(, ). That probably means an 
> empty or invalid value. Not a real improvement over the string...
>
> I have hacked around the issue for now by multiplying the value I am 
> after in my query, and deviding it by the same value again after 
> retreiving it. Still, this is an extremely ugly hack, and I'd like to 
> get rid of it...
>
> André
>
>
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>   
Can I get you to check the lastError() when it returns a null variant?
Looks like it's possibly getting an error.
Looks suspiciously like an Access via odbc bug. I'll try and get a
system up sometime this week and see if I can't take a squiz at it.

-- 
Bill King, Software Engineer
Qt Development Frameworks, Nokia Pty Ltd
Brisbane Office

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