RE: [sqlalchemy] Re: To select only some columns from some tables using session object, relation many-to-many

2010-08-04 Thread King Simon-NFHD78 
Alvaro Reinoso wrote:
 
 It works out, thank you! How could I just retrieve some columns from
 both tables? For example, if I try to select some columns from Item
 and Channel, I get class 'sqlalchemy.util.NamedTuple' when I'd
 like to get a channel type with its items:
 
 result = session.query(Channel.title,
 Item.title).join('items').filter(Item.typeItem == zeppelin/
 channel).order_by(Channel.titleView).all()
 
 I just need some values many times, I don't need to retrieve the whole
 object.
 
 Thanks in advance!
 

It sounds like you are looking for deferred column loading:

http://www.sqlalchemy.org/docs/mappers.html#deferred-column-loading

You can mark certain columns as not to be loaded until they are
accessed. This can be done at mapper definition time as well as at query
time.

Hope that helps,

Simon

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[sqlalchemy] Re: To select only some columns from some tables using session object, relation many-to-many

2010-08-03 Thread Alvaro Reinoso 
It works out, thank you! How could I just retrieve some columns from
both tables? For example, if I try to select some columns from Item
and Channel, I get class 'sqlalchemy.util.NamedTuple' when I'd
like to get a channel type with its items:

result = session.query(Channel.title,
Item.title).join('items').filter(Item.typeItem == zeppelin/
channel).order_by(Channel.titleView).all()

I just need some values many times, I don't need to retrieve the whole
object.

Thanks in advance!


On Aug 3, 1:40 am, Kalium raymond.ma...@gmail.com wrote:
 On Aug 3, 8:43 am, Alvaro Reinoso alvrein...@gmail.com wrote:



  Hello,

  I have these classes where items (class Item) is related to channel
  object. Channel can contain many items:

  channel_items = Table(
          channel_items,
          metadata,
          Column(channel_id, Integer,
              ForeignKey(channels.id)),
          Column(item_id, Integer,
              ForeignKey(Item.id))
      )

  class Channel(rdb.Model):
      rdb.metadata(metadata)
      rdb.tablename(channels)

      id = Column(id, Integer, primary_key=True)
      title = Column(title, String(100))

      items = relation(Item, secondary=channel_items,
  backref=channels)

  class Item(rdb.Model):
      rdb.metadata(metadata)
      rdb.tablename(items)

      id = Column(id, Integer, primary_key=True)
      title = Column(title, String(100))

  I know how to get all the columns using something like:

  session = rdb.Session() channels =
  session.query(Channel).order_by(Channel.title)

  However, I'd like to select some columns from both tables with some
  conditions in Item. For example, select all the channels where
  item.type = 'jpg'. I'd like to get a channel object with items
  attributes with that condition for example. How can I do that?

  I've tried something like (no one worked out):

  result = session.query(Channel).filter(Item.typeItem != 'zeppelin/
  channel').all()
  result = session.query(Channel, Item).filter(Item.typeItem !=
  'zeppelin/channel').all()

  Thanks in advance!

 Try something like

 session.query(Channel).join('items').filter(Item.typeItem !=
 'whatever').all()

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[sqlalchemy] Re: To select only some columns from some tables using session object, relation many-to-many

2010-08-02 Thread Kalium 


On Aug 3, 8:43 am, Alvaro Reinoso alvrein...@gmail.com wrote:
 Hello,

 I have these classes where items (class Item) is related to channel
 object. Channel can contain many items:

 channel_items = Table(
         channel_items,
         metadata,
         Column(channel_id, Integer,
             ForeignKey(channels.id)),
         Column(item_id, Integer,
             ForeignKey(Item.id))
     )

 class Channel(rdb.Model):
     rdb.metadata(metadata)
     rdb.tablename(channels)

     id = Column(id, Integer, primary_key=True)
     title = Column(title, String(100))

     items = relation(Item, secondary=channel_items,
 backref=channels)

 class Item(rdb.Model):
     rdb.metadata(metadata)
     rdb.tablename(items)

     id = Column(id, Integer, primary_key=True)
     title = Column(title, String(100))

 I know how to get all the columns using something like:

 session = rdb.Session() channels =
 session.query(Channel).order_by(Channel.title)

 However, I'd like to select some columns from both tables with some
 conditions in Item. For example, select all the channels where
 item.type = 'jpg'. I'd like to get a channel object with items
 attributes with that condition for example. How can I do that?

 I've tried something like (no one worked out):

 result = session.query(Channel).filter(Item.typeItem != 'zeppelin/
 channel').all()
 result = session.query(Channel, Item).filter(Item.typeItem !=
 'zeppelin/channel').all()

 Thanks in advance!

Try something like

session.query(Channel).join('items').filter(Item.typeItem !=
'whatever').all()

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