[Qt-interest] Variants and Binds

[Tony Rietwyk]

I have no idea what the Qt Oracle driver does.  It should be able to
transfer date/time values into the database without converting them to or
from string.  

to_char is an Oracle function, and has nothing to do with Qt. 

Tony.


> -----Original Message-----
> From: Jason H [mailto:scorp1us at yahoo.com] 
> Sent: Thursday, 24 September 2009 10:54
> To: Tony Rietwyk; qt-interest at trolltech.com
> Subject: Re: [Qt-interest] Variants and Binds
> 
> 
> It does help, but where does the "to_char('2001-01-01', 
> 'YYYY-MM-DD')" come from? I learned that was being done from 
> from boundValues()
> 
> 
> 
> ----- Original Message ----
> From: Tony Rietwyk <tony.rietwyk at rightsoft.com.au>
> To: qt-interest at trolltech.com
> Sent: Wednesday, September 23, 2009 8:45:54 PM
> Subject: Re: [Qt-interest] Variants and Binds
> 
> Jason wrote:
> 
> > I wish to add a new kind of class to QVariant, so that I can 
> > use it in a SQL bind.
> > 
> > Specifically, I need to provide access to database 
> > expressions. For  instance a QDate object is serialized to 
> > to_char('2001-01-01', 'YYYY-MM-DD') when used in Oracle. I 
> > need to provide a very similar thing in that I need 
> > SEQUENCE.nextval (an expression, not a string) so that my 
> > call is bindValue(":rowid", 
> > Expression("TABLE_ID_SEQUENCE.nextval")); If I use a 
> > QByteArray, I get "TABLE_ID_SEQUENCE.nextval", the string, 
> > and that isn't a valid numeric record ID. 
> > 
> > So I need to know how I can create  a datatype that won't 
> be quoted. 
> > 
> > Thanks!
> 
> Hi Jason, 
> 
> Even if you did add the extra type to QVariant, it would not 
> work.  A SQL
> expression can only be evaluated on the server, and you can 
> only bind values
> on the client.  
> 
> I think you can either: 
> 
> - Put the expression into the actual SQL statement, for 
> example, insert into
> tableName(fieldName1, fieldName2...) values 
> (TABLE_ID_SEQUENCE.nextval,
> :fieldName2...)
> 
>     Then just bind the other fields. 
> 
> - Or you need to explicitly select the value from the sequence first: 
> 
>     myQuery.exec("select TABLE_ID_SEQUENCE.nextval from dual");
>     myQuery.next();
>     int sequence = myQuery.value(0).toInt;
> 
> then bind that value just like the fields.  
> 
> Hope that helps, 
> 
> Tony.