Many thanks Robert :) I found some examples of chained joins later
while using the manual as a sleep aid
but your explanation is clearer.
Cheers!
--Peter
At 04:19 16.4.06, Robert Leftwich wrote:
Peter L. Buschman wrote:
Apologies since this seems like a basic question, but what is the
best practice syntax for performing
multiple joins against a single table? The documentation examples
clearly demonstrate how to join
2 tables together, but examples with 3 or more are unclear.
For example, it seemed like this should work:
query = select([table1, table2, table3], ((table1.c.foo_id ==
table2.c.foo_id) and (table2.c.bar_id == table3.c.bar_id)))
Using and_() should do the trick here:
query = select([table1, table2, table3], and_(table1.c.foo_id ==
table2.c.foo_id, table2.c.bar_id == table3.c.bar_id))
or perhaps more explicitly/verbosely (as shown in the Inner and
Outer Joins section of the documentation -
http://www.sqlalchemy.org/docs/sqlconstruction.myt#constructing_join
query = select([table1, table2, table3], from_obj=[
table1.join(
table2, table2.c.foo_id==table1.c.foo_id).join(
table3, table3.c.bar_id==table2.c.bar_id)
])
HTH
Robert
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