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Hi.
When selecting against joined tables, SQLAlchemy always use the
"ON join_condition" form.
The problem with this is that when the joined columns have the same
name, they are included 2 times in the result set.
Example (PostgreSQL):
CREATE TABLE foo (
id TEXT PRIMARY KEY,
x INTEGER
);
CREATE TABLE bar (
a INTEGER PRIMARY KEY,
id TEXT REFERENCES (foo.id) NOT NULL
);
INSERT INTO foo VALUES ('ID', 777);
INSERT INTO bar VALUES (0, 'ID');
SELECT * FROM foo JOIN bar ON foo.id = bar.id;
id | x | a | id
- ----+-----+---+----
ID | 777 | 0 | ID
If we use "USING ( join_column [, ...] )", instead, only one of each
pair of equivalent columns will be included in the join output, not both.
SELECT * FROM foo JOIN bar USING (id);
id | x | a
- ----+-----+---
ID | 777 | 0
Is it possible to change SQLAlchemy to use the second form when the
joined columns have the same name?
In alternative, this can be requested explicitly, as example:
class Join(FromClause):
__visit_name__ = 'join'
def __init__(self, left, right, onclause=None, using=None,
isouter=False):
...
When specified ``using`' take precedence over `onclause`.
Thanks Manlio Perillo
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