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Re: Difficulty modelling sales taxes

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On Mon, Jan 2, 2017 at 9:58 AM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote:
On 01/02/2017 06:38 AM, Melvin Davidson wrote:

On Mon, Jan 2, 2017 at 6:29 AM, Frank Millman <frank@xxxxxxxxxxxx
<mailto:frank@xxxxxxxxxxxx>> wrote:


    *From:* amul sul
    *Sent:* Monday, January 02, 2017 12:42 PM
    *To:* Frank Millman
    *Cc:* pgsql-general
    *Subject:* Re: Difficulty modelling sales taxes

    > On Mon, Jan 2, 2017 at 4:03 PM, Frank Millman <frank@xxxxxxxxxxxx
    <mailto:frank@xxxxxxxxxxxx>> wrote:
    >
    > Hi all
    >
    >
    >
    > It is a bit ugly, because I have to use the ‘NVARCHAR code’ column from
    >
    > tax_codes, not the primary key, but I think it would work.
    >
    >
    >
    NVARCHAR ?  Are you using PostgreSQL as database server?
    >


    Oops, sorry.

    I am testing with PostgreSQL and with SQL Server, so I was in the
    wrong mindset when I posted.

    I should have said VARCHAR.

    Frank





*First, there is no need to make row_id's when you already have a valid
primary key.

In a perfect world yes, but this is a world with ORM's as I found out the hard way:

https://docs.djangoproject.com/en/1.10/ref/models/fields/#primary-key

"The primary key field is read-only. If you change the value of the primary key on an existing object and then save it, a new object will be created alongside the old one."



--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx

>https://docs.djangoproject.com/en/1.10/ref/models/fields/#primary-key
You are quoting from a django document.  Please don't muddle the waters.
So you are saying this will not work?
UPDATE mytable
  SET mykey = 'new_value'
  WHERE mykey = 'old_value';

DELETE FROM mytable
  WHERE mykey = 'old_value';

Happy New Year Adrian

--
Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.


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