On Thu, Dec 1, 2011 at 4:31 AM, Anthony <[email protected]> wrote:
> On Wednesday, November 30, 2011 5:41:34 PM UTC-5, Chandra wrote:
>>
>> I'm going through the official book, currently at the DAL chapter. I'm
>> having confusions over query and set objects.
>>
>> for e.g.
>> 1. To fetch rows one uses , rows = db(db.mytable.myfield!=None).select()
>> it returns a collection of rows, that is fine. But, what is a
>> 'set' then? Isn't 'rows' itself a set of records?
>>
>
> A Set defines a set of records but doesn't actually select them from the
> db -- so it's like a conceptual representation of the records, but not the
> records themselves. When you apply the select() method to the Set, you
> actually pull the records from the database and transform them to a Python
> object (a Rows object). The distinction is useful because Sets have other
> methods besides select(), such as update(), count(), and delete().
>
>
This makes things clear now.
>
>> 2. A query object represents a sql 'where' clause like, myquery =
>> (db.mytable.myfield != None) | (db.mytable.myfield > 'A')
>> Can't the same thing be done like, rows =
>> db((db.mytable.myfield!=None) | (db.mytable.myfield >'A'))
>> what is the need of having a query object?
>>
>
> What is your proposed alternative?
>
> using, myset = db((db.mytable.myfield!None)|(db.mytable.myfield>'A')) and
then
rows = myset.select()
will do the same thing, will it? so that we can skip two lines , one
defining the myquery(db.mytable.myfield!None)|(db.mytable.myfield>'A'),
then calling myset=db(myquery)
