Could cast be defined to allow string values (i.e. cast(...,
"Numeric(14,2)")? This would fix my problem. Guess I will check the code
and see.
On Sun, Mar 22, 2009 at 12:00 PM, Shawn Church
<sh...@schurchcomputers.com>wrote:
>
>
> On Sun, Mar 22, 2009 at 8:17 AM, Michael Bayer
> <mike...@zzzcomputing.com>wrote:
>
>>
>> theres three layers to this issue. the first is, yes as_scalar() is
>> trying to compile the expression which I don't think there's a very
>> good reason, so ill likely commit a change for that (it will result in
>> a behavioral change regarding the namespace of "someselect.c" but im
>> hoping not one anyone was relying upon that).
>
>
> Sounds good
>
>
>> the second layer is,
>> if you're casting against a constant value like below, or a column on
>> the Order class, you don't need the select() - just say
>> cast(...).label('foo') -
>
>
> I'm not casting a constant (see below). I just simplified the expression
> until I found the specific function causing the error.
>
> however, convenient operations like "print
>> query" still wont work since they evaulate the cast() without a
>> dialect.
>
>
> I like using print for debugging but I can live without it.
>
>
>> the third is, the whole "cast can't compile without a
>> dialect" thing is going away in 0.6, but I can't make it work in 0.5
>> without major changes.
>>
>> One particular workaround that would totally eliminate the issue until
>> 0.6 comes out would be to use the dialect-specific type for now, i.e.
>> MSNumeric (mysql), PGNumeric (postgres), SLNumeric (sqlite).
>>
>>
> I'm using SQLIte for unit tests and MySQL for production so I can't see a
> way to do this.
> I found that I CAN cast the result of the select (references OrderLine
> table, not shown):
>
> def IF(condition, true, false):
> return case([(condition, true)], else_ = false)
>
>
> class Order(Base):
>
> -- Skipping Column Definitions --
>
> L = OrderLine
>
> taxable = column_property(
> cast(select([func.sum(IF(L.taxable, L.quantity * L.price, 0))],
> L.order_id == id).as_scalar(),
> Numeric(14.2)).label("taxable"))
>
>
> This isn't really the same thing because the float would be rounded after
> the sum not line by line. I think I could also use sum(... type_ =
> Numeric(14,2)) for the same result. Am I missing an easier way to do this?
>
>
>>
>>
>> On Mar 22, 2009, at 6:27 AM, Shawn Church wrote:
>>
>> > >>> import sqlalchemy
>> > >>> sqlalchemy.__version__
>> > '0.5.2'
>> >
>> > >>> from sqlalchemy import *
>> > >>> from sqlalchemy.orm import relation, column_property,
>> > sessionmaker
>> >
>> > >>> from sqlalchemy.ext.declarative import declarative_base
>> > >>> Base = declarative_base()
>> > >>> Session = sessionmaker()
>> >
>> > >>> class Order(Base):
>> > ... __tablename__ = "orders"
>> > ...
>> > ... id = Column(Integer, primary_key = True)
>> > ...
>> > ... test = column_property(select([cast(1,
>> > Numeric(14,2))]).label("test"))
>>
>>
>> >>
>>
>
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