> > heh, i don't have a vague idea what it should be.
>
> because you dont want to learn SQL. but if youre really trying to
> write a one-person system on the scale of complexity of SAP, which
> usually have...i dunno, several hundred developers for many years ?
> i think youre gonna have to.
learning SQL and learning how to use SQL are diff.things. Many ppl
know python but few actualy _know_ it. i don't want to _know_ sql -
e.g. the way u do.
> > i see at web that what i'm describing is called self-join.
> > So basicaly, self-referential/self-joining queries cannot be done
> > in SA?
>
> the only query that SA explicitly says "no" to is a
> self-referential eager load. the rest, it will try and see how
> far it gets. all ORMs require you to hand-code queries for
> criterions that are too complicated.
i think i managed to construct a proper thing, changing
PropertyLoader.get_join(), and made my own join_via():
PropertyLoader.get_join():
.....
#add these before the secondaryjoin is and-ed:
if parent is self.mapper:
self_select_table = self.mapper.select_table.alias()
primaryjoin.accept_visitor( sql_util.ClauseAdapter(
self_select_table, equivalents=parent_equivalents,
exclude=self.foreignkey, #noidea is it exclude or
include or what
))
....
join_via(): tracking/returning also the last used sub_clause/mapper
and then (from the last_sub_clause) somehow reaching the target
aliased column and use its table as base of the comparison:
...........
via_names = hierarchname[1:-1]
last_attr = hierarchname[-1]
clause, lastmapper, lastsubclause = join_via( via_names, mapper0)
lastcol = lastmapper.prop[ last_attr]
lastrefofclause = lastsubclause.right
if isinstance( lastrefofclause.table, sql.Alias):
lastcol = lastcol._make_proxy( lastrefofclause.table )
return clause, lastcol
## and now eventualy and_ the clause and lastcol
.........
The last-referred-aliased-table picking above is flaky, cannot make
anything better for now - unless interface of get_join() is also
changed to return that explicitly..
Any idea to incorporate such/similar functionality in SA? Probably
with more stuff going on around polymorph-unions, secondary-joins
etc.
> >> On Feb 15, 9:41 am, svilen <[EMAIL PROTECTED]> wrote:
> >>> and, how u make the (3) or (4) work?
> >>> aliasing the table.column in the comparison does not help.. it
> >>> should be aliased somehow inside the join also..
> >>>
> >>> Here a simpler case, without the inheritance.
> >>> 3 and 4 do not work here too - one does exception, other return
> >>> nothing.
> >>>
> >>> maybe express the query in another way? how?
> >>>
> >>> ciao
> >>> svil
> >>>
> >>>> taking a look, i think what you should do is use an alias of
> >>>> the table_Employee in your queries. since the engineer mapper
> >>>> is using joined table inheritance, the default table_Employee
> >>>> is already going to be involved in the query, so your external
> >>>> join condition needs to be off a distinct alias of it to
> >>>> prevent mixups.
> >>>
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