Re: [CDBI] question about set_sql and iterators

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On Thu, Nov 19, 2009 at 4:45 AM, <arnim.rupp-5Wlsihp/[email protected]> wrote:

> > I don't think you've really understood how object-relational mappers
> > work.
>
> i would say it's more a question if there can be just one database-table
> in one class. as soon as I use set_sql to select from 2+ tables that's
> not the case anyway.
>

Yes, one class is one "table", but there's lots of options.

You could define a view in your database and then create a class for the
view just like any other table.  Probably won't be able to update w/o more
database help.

You can create very complex queries with set_sql, and use TEMP columns as
pointed out.  IIRC, you don't even need TEMP column if you pass the object
to something like Template Toolkit (which I hope you are) because it can
treat it like a hash.  That should drive OO purest nuts.

If you don't care about relationships and just want to display the result
you can use set_sql and then get an $sth with $object->sql_<name used in
se_sql> and then use standard DBI and return whatever data structure you
want.  I do that all the time for complex pages that need to be optimized
for speed.

If you need all the relationships you can use the above to fetch $sth and
normal DBI and then construct your objects however you wish (Yes, I've done
this).

Finally, there's Class::DBI::Sweet where you can specify prefetch similar to
DBIx::Class that wlll do the joins for your and build the objects.  This is
useful if your custom SQL is really there just for the join.
Class::DBI::Sweet adds a lot of useful features somewhat similar to
DBIx::Class but with CDBI you still have lazy column loading and things like
$cd->artist->id won't trigger a separate database query.



-- 
Bill Moseley
[email protected]

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<br><br><div class=3D"gmail_quote">On Thu, Nov 19, 2009 at 4:45 AM,  <span =
dir=3D"ltr">&lt;<a href=3D"mailto:arnim.rupp-5Wlsihp/[email protected]">arnim.rupp@lhsy=
stems.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=
=3D"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; p=
adding-left: 1ex;">

<div class=3D"im">&gt; I don&#39;t think you&#39;ve really understood how o=
bject-relational mappers<br>
&gt; work.<br>
<br>
</div>i would say it&#39;s more a question if there can be just one databas=
e-table<br>
in one class. as soon as I use set_sql to select from 2+ tables that&#39;s<=
br>
not the case anyway.<br></blockquote><div><br>Yes, one class is one &quot;t=
able&quot;, but there&#39;s lots of options.<br><br>You could define a view=
 in your database and then create a class for the view just like any other =
table.=A0 Probably won&#39;t be able to update w/o more database help.<br>

<br>You can create very complex queries with set_sql, and use TEMP columns =
as pointed out.=A0 IIRC, you don&#39;t even need TEMP column if you pass th=
e object to something like Template Toolkit (which I hope you are) because =
it can treat it like a hash.=A0 That should drive OO purest nuts.<br>

<br>If you don&#39;t care about relationships and just want to display the =
result you can use set_sql and then get an $sth with $object-&gt;sql_&lt;na=
me used in se_sql&gt; and then use standard DBI and return whatever data st=
ructure you want.=A0 I do that all the time for complex pages that need to =
be optimized for speed.<br>

<br>If you need all the relationships you can use the above to fetch $sth a=
nd normal DBI and then construct your objects however you wish (Yes, I&#39;=
ve done this).<br><br>Finally, there&#39;s Class::DBI::Sweet where you can =
specify prefetch similar to DBIx::Class that wlll do the joins for your and=
 build the objects.=A0 This is useful if your custom SQL is really there ju=
st for the join.=A0 Class::DBI::Sweet adds a lot of useful features somewha=
t similar to DBIx::Class but with CDBI you still have lazy column loading a=
nd things like $cd-&gt;artist-&gt;id won&#39;t trigger a separate database =
query.<br>

<br><br></div></div><br>-- <br>Bill Moseley<br><a href=3D"mailto:moseley@ha=
nk.org">[email protected]</a><br>

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