I have a situation where I can have an arbitrary number of subqueries that
need to be joined on the last step, except if the number of queries, n, is
1.
For example, for n = 1, suppose I have a complex query set to the variable
A[1]
The final submitted query would then look like:
query = db.session.query(label('sid',
distinct(A[1].c.patient_sid)))
Easy enough!
Now, suppose, I have two complex queries, A[1] and A[2] that are then
joined as such:
query = db.session.query(label('sid',
distinct(A[1].c.patient_sid))). \
join(A[2],A[2].c.patient_sid==a[1].c.patient_sid)
Not too bad...
Now, I have an arbitrary number of complex queries, A[1]...A[n] that need
to be joined:
query = db.session.query(label('sid',
distinct(A[1].c.patient_sid))). \
join(A[2],A[2].c.patient_sid==a[1].c.patient_sid). \
....
join(A[n],A[n].c.patient_sid==a[1].c.patient_sid)
The above works fine, when I have conditionals based on the number n of
queries, e.g.,
if (n == 1):
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid)))
if (n == 2):
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid))). \
join(a[2],a[2].c.patient_sid==a[1].c.patient_sid)
if (n == 3):
query = db.session.query(label('sid',
distinct(a[1].c.patient_sid))). \
join(a[2],a[2].c.patient_sid==a[1].c.patient_sid). \
join(a[3],a[3].c.patient_sid==a[1].c.patient_sid)
etc., but since I can have an arbitrary number of these queries that need
to be joined, not only is use of conditionals to set up the correct form of
my join inefficient, it is highly redundant and would be a huge mess.
Thus, I am wondering if it is possible to construct my join somehow, like:
if (n == 1):
query = 'db.session.query(label('sid',
distinct(a[1].c.patient_sid)))'
elif (n > 1):
query = 'db.session.query(label('sid',
distinct(a[1].c.patient_sid)))'
for i in range (0,n)
query += '.join(A[i],A[i].c.patient_sid==a[1].c.patient_sid)'
eval(query)
I've tried all sorts of crazy things, but cannot get the general case to
work.
Thanks in advance!
Greg--
--
Greg M. Silverman
Senior Developer Analyst
Cardiovascular Informatics <http://www.med.umn.edu/cardiology/>
University of Minnesota
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