I'm having trouble envisaging how to implement some basic many-to-many
features; ones that would be trivial with a couple of INNER JOINs in
normal SQL but which are baffling me in SQLObject.
My basic structure is as follows (cut down from a full TurboGears application):
class User(SQLObject):
skills = MultipleJoin("Skill", joinColumn="user_id")
... etc ...
class Skill(SQLObject):
"""An instance of a skill that a particular user claims to have."""
user = ForeignKey("User")
stype = ForeignKey("Skilltype")
competence = IntCol()
class Skilltype(SQLObject):
"""A type of skill, which can be held by many users, to different
degrees of competence"""
name = UnicodeCol(length=255)
...etc....
The Skill table links the User table to the Skilltype table. I can't
use an implicit intermediate table as I need access to the
'competence' column, and may add other columns later.
The "How can I define my own intermediate table in my Many-to-Many
relationship?" entry in the docs looks vaguely like what I might need,
but it gives no examples of how to use the resulting objects.
So, how would I implement queries like the following?
# All User 1's skills where competence > 3
SELECT * from User INNER JOIN Skill USING (user_id) INNER JOIN
Skilltype USING (stype_id) WHERE user_id = 1 AND Skilltype.competence
> 3
Or...
# All users who have the Skill "xyz"
SELECT * from User INNER JOIN Skill USING (user_id) INNER JOIN
Skilltype USING (stype_id) WHERE Skilltype = "xyz" GROUP BY User
--
Ben Sizer
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