On Dec 2, 2010, at 5:30 AM, Андрей wrote:
> Hello.
> There is an example (found in
> http://discorporate.us/jek/talks/pgwest08-sqlalchemy.pdf)
>
>>>> sql = r'''
> ... SELECT *
> ... FROM ticket JOIN ticket_change
> ... ON (ticket.id = ticket_change.ticket)
> ... WHERE summary ~ '[[:digit:]]+'
> ... ORDER BY ticket.time desc
> ... LIMIT 1
> ... '''
>>>> session.query(Ticket, Change).from_statement(sql).first()
> Traceback (most recent call last):
> ...
> InvalidRequestError: Ambiguous column name 'time'
> in result set! try 'use_labels' option on select statement.
>
> And as its solution provides the following example:
>
>>>> q3 = session.query(Ticket, Change) \
> .select_from(tickets.join(ticket_changes)) \
> .filter(Ticket.id==1) \
> .order_by(desc(Change.time))
>>>> print q3
> SELECT ticket.id AS ticket_id, ...
> ticket_change.ticket AS ticket_change_ticket, ...
> FROM ticket JOIN ticket_change
> ON ticket.id = ticket_change.ticket
> WHERE ticket.id = %(id_1)s
> ORDER BY ticket_change.time DESC
>>>> q3.first()
> (Ticket(1, 'document arguments for table, column, ...'),
> Change(1, 1149120761, 'status', 'closed'))
>
> So can we all still use from_statement for raw queries where there are
> joining exists.
> Maybe there are some ways to add some labels in query ?
when from_statement() is used, columns can be in one of two forms:
select a, b from table
or
select a as table_a, b as table_b from table
where the latter version disambiguates column names based on their table or
alias of origin. If you have a select() construct, calling "s =
s.apply_labels()" will produce this effect for the select() construct itself.
>
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