Hi Michael,
many thanks for your help!
Is there any way to do this in an automatic way? I mean now i have the
following code
from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
MaPMTs = Table('MaPMTs',Base.metadata,
Column('id',Integer,primary_key=True),
Column('Serial_Number',String),
Column('Gain',Float),
Column('Validity_Start',DateTime,default=func.now()),
Column('Validity_End',DateTime),
)
class MaPMTs(Base):
__table__ = MaPMTs
from sqlalchemy import create_engine
engine = create_engine('postgres://localhost/DB')
from sqlalchemy.orm import sessionmaker
DBSession = sessionmaker()
DBSession.configure(bind=engine)
and i obtain for example this table
ID Serial_Number Gain
Validity_Start Validity_End
1; “FA0026”; 1.18;
"2014-11-27 11:16:36.779973”; "2014-11-27
11:18:44.91704"
2; ”FA0026”; 1.08;
"2014-11-27 11:18:44.91704";""
typing on shell
>>> s=DBSession()
>>> tube1=MaPMTs(Serial_Number='FA0026',Gain=1.18)
>>> s.add(tube1)
>>> s.commit()
>>> tube2=MaPMTs(Serial_Number='FA0026',Gain=1.08)
>>> s.add(tube2)
>>> s.commit()
>>> tube1_update =
>>> s.query(MaPMTs).filter(MaPMTs.Serial_Number=='FA0026').first()
>>> tube1_update.Validity_End = tube2.Validity_Start
>>> s.commit()
I would obtain the same table without invoke a query. Is it possibile to add
some new lines in the code to do the same thing?
Giovanni
> Il giorno 27/nov/2014, alle ore 01:18, Michael Bayer
> <mike...@zzzcomputing.com> ha scritto:
>
> idiomatically this would be:
>
> tube1 = session.query(Phototubes).filter(<get the first object>).one()
> tube2 = Phototubes(gain = new_gain, transactiondate = tube1.transactiondate,
> serialnumber=tube1.serialnumber)
> session.add(tube2)
> session.commit()
>
>
> That’s a SELECT then an INSERT. In the event that you’re looking for
> something more exotic than that (like, an INSERT that embeds the SELECT) let
> us know.
>
>
>> On Nov 26, 2014, at 5:37 AM, joecav...@hotmail.it
>> <mailto:joecav...@hotmail.it> wrote:
>>
>> Hello,
>>
>> i'm new on sqlalchemy and i have a problem.
>> I want to update the entry in a column of a table of a row using the info of
>> a new row. For example, i could have measured a value in a certain date
>>
>> class Phototubes(Base):
>> __tablename__ = 'MaPMTs'
>> SerialNumber = Column(String, primary_key=True)
>> Gain = Column(Float)
>> TransactionDate = Column(
>> DateTime,
>> default=func.now())
>> )
>>
>> Now, I would add a column "End_Of_Validity = Column(DateTime)" so that if I
>> measure a new value of the Gain of the same phototube (so I add a new row
>> with the same SerialNumber but different value of Gain) I can update the
>> previous entry of column End_Of_Validity with this TransactionDate
>> (otherwise empty). How can I do this?
>> Many Thanks,
>> Giovanni
>>
>>
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