Re: [sqlalchemy] Re: Dynamically constructing joins
Ha! Ha! On my previous attempts, I had something similar to this, but
instead, I had
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
if (n 1):
for table in join_tables[1:]:
for criterion in join_criteria[1:]:
query = query.join(eval(table), eval(criterion))
Where the variables table and criterion were built lists, so that I ended
up doing a Cartesian product of all my tables, which was giving me many
problems, with aliasing being the least of it!
Thanks!
Greg--
On Tue, Mar 24, 2015 at 11:22 PM, Jonathan Vanasco jonat...@findmeon.com
wrote:
any reason why you're not building a query like this?
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
if n = 2
query = query.\
join(a[2],a[2].c.patient_sid==a[1].c.patient_sid)
if n = 3
query = query.\
join(a[3],a[3].c.patient_sid==a[1].c.patient_sid)
or
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
for i in range(2, n):
query = query.\
join(a[i],a[i].c.patient_sid==a[1].c.patient_sid)
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Greg M. Silverman
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Cardiovascular Informatics http://www.med.umn.edu/cardiology/
University of Minnesota
612-626-0919
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[sqlalchemy] Re: Dynamically constructing joins
Yeah, there's no reason to touch eval -- and a lot of reasons not to. Security issues aside, when you make a mistake the error will be completely unintelligible. You can create joins dynamically very easily by just iteratively building up on it, and using getattr() if needed. If you're doing any advanced things (subqueries, aliases, etc), I would suggest keeping the online docs loaded in a browser window and paying close attention to the return values. Most operations will return a query, but a few will return another object. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] Re: Dynamically constructing joins
eval() was definitely not doing what I expected. Thanks for the tip about getattr(), and thanks for helping get my head screwed on right! Greg-- On Wednesday, March 25, 2015 at 11:33:44 AM UTC-5, Jonathan Vanasco wrote: Yeah, there's no reason to touch eval -- and a lot of reasons not to. Security issues aside, when you make a mistake the error will be completely unintelligible. You can create joins dynamically very easily by just iteratively building up on it, and using getattr() if needed. If you're doing any advanced things (subqueries, aliases, etc), I would suggest keeping the online docs loaded in a browser window and paying close attention to the return values. Most operations will return a query, but a few will return another object. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] Re: Dynamically constructing joins
any reason why you're not building a query like this?
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
if n = 2
query = query.\
join(a[2],a[2].c.patient_sid==a[1].c.patient_sid)
if n = 3
query = query.\
join(a[3],a[3].c.patient_sid==a[1].c.patient_sid)
or
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
for i in range(2, n):
query = query.\
join(a[i],a[i].c.patient_sid==a[1].c.patient_sid)
--
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