On Jun 2, 2012, at 10:49 PM, Db wrote:
> I have following class
>
> class stockhistory(DeclarativeBase):
> __tablename__ = 'stockhistory'
> __table_args__ = {}
> #column definitions
> shrno = Column(u'shrno', BIGINT(), primary_key=True)
> sprice = Column(u'sprice', FLOAT())
> sstockex = Column(u'sstockex', VARCHAR(length=10))
> ssymbol = Column(u'ssymbol', VARCHAR(length=10))
> svolume = Column(u'svolume', BIGINT())
>
>
> and a query which works fine and output is later
> displayed in an paginated datagrid :
>
> data = session.query(stockhistory).filter_by(ssymbol =
> muid).order_by(desc('shrno')).limit(1000).all()
>
> Now I want to improve the query by having the sprice column return
> a precision of 2 decimal places.
>
> In raw sql (Firebird) I would do this like :
>
> cast(sprice as decimal(18,2)) as sprice
>
> in sqlalchemy it maybe:
>
> cast(sprice,Numeric(18,2))
>
> but how to tell this to above query eludes me.
your options are:
at query time, individually:
session.query(stockhistory, cast(stockhistory.sprice, Numeric(18,
2)).label('sprice_numeric'))
at mapper time:
class stockhistory(..):
...
sprice_numeric = column_property(cast(sprice, Numeric(18, 2)))
using a combination:
class stockhistory(..):
...
sprice_numeric = deferred(cast(sprice, Numeric(18, 2)))
session.query(stockhistory).options(undefer('sprice_numeric'))
http://docs.sqlalchemy.org/en/rel_0_7/orm/mapper_config.html#using-column-property
http://docs.sqlalchemy.org/en/rel_0_7/orm/mapper_config.html#deferred-column-loading
>
>
> Thanks for any ideas.
>
>
>
>
>
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