Re: [cx-oracle-users] Null value converts to python None and when used for update converts to string 'None'

[Anurag C. <anu...@gm...>]

Thanks Jani...With that my issue is solved.

Regards
Guddu


On Tue, Apr 2, 2013 at 1:35 AM, Jani Tiainen <re...@gm...> wrote:

> 2.4.2013 5:51, Anurag Chourasia kirjoitti:
> > *Dear friends...Could you please help me with this issue?*
> >
> > *Steps to reproduce?*
> > 1. Fetch the value of a varchar2 column that has Null as its current
> value.
> > 2. Use the fetched value to update any table's column.
> >
> > *Expected output?*
> > Instead of updating to Null, the table column gets updated to a string
> value of 'None'
> >
> > *Version in use*
> > Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit
> (Intel)] on win32
> > cx_Oracle - 5.1.2
> > Oracle 11G
> >
> > *Additional information*
> >
> > This could be because in the update query, I am using '%s' format....for
> example
> >
> > cursor.execute("UPDATE EMP SET NAME='%s'" %(None))
> >
> > But there is no other way. If i simply use
> >
> > cursor.execute("UPDATE EMP SET NAME=%s" %(None)) then I get a syntax
> error.
> >
> > There should be a way to update a column to NULL
>
> Why are you trying to inject data instead of using standard Python API
> to do things right?
>
> If you persists constructing query string completely by hand (like you
> have done), then you have to take care of NULL by yourself.
>
> In most cases following works better:
>
> cursor.execute('UPDATE EMP SET NAME=:arg1', {'arg1' : None })
>
> When you do it that way Python DB-API takes care of correct quotation
> and makes sure that there is no way to inject malicious data and in most
> cases correct datatype conversion takes a place (there is few occassions
> when this fails)
>
> cx_Oracle doesn't support %s format, it supports only :name (named)
> format [1].
>
> [1] http://www.python.org/dev/peps/pep-0249/#paramstyle
> --
> Jani Tiainen
>
> - Well planned is half done and a half done has been sufficient before...
>
>
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