# Help!

**URL:** <https://www.ruby-forum.com/t/help/96914>\
**Category:** Rails\
**Created:** [July 3, 2006, 12:40pm UTC](https://www.ruby-forum.com/t/help/96914 "2006-07-03T12:40:37Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 3, 2006, 12:40pm UTC](https://www.ruby-forum.com/t/help/96914/1 "2006-07-03T12:40:37Z")

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Hi,

i’m fairly new to ruby on rails, and i know the question at hand may  
seem simple at first, but i’m getting really caught up in trying to  
understand this and the docs aren’t giving me answer. i actually thought  
i knew how the sql commands work (like :include, :conditions, :etc) but  
obviously, i don’t.

there are three models M1, M2, M3 joined by a habtam relashinship of

M1 has\_and\_belongs\_to\_many M2  
M2 has\_and\_belongs\_to\_many M1  
M2 has\_and\_belongs\_to\_many M3  
M3 has\_and\_belongs\_to\_many M2

and a MyController which is the backbone of the site. (although i  
haven’t specified exactly {model :M1} or something like that in the  
controller, but as far as i know, that shouldn’t change anything [?]).

in MyController i have an action that selects rows from M1 with an  
:include =\> ‘M2s’ and that changes the sql output to “outer left  
join…etc” which is great. . . but when i want to add a :conditions  
clause, i find that it doesn’t add the conditon correctly into the outer  
left join sql command, and it ends up giving me an sql syntax error!  
If i try to use the :conditions clause alone (without :include) , i get  
no error, which is great.  
🙂

but how do i get the two together?? isn’t it possible to put a  
:condition on a select[habtam] action? am i missing something entirely,  
or is there something small i am missing? maybe i need to define  
something in the controller regarding the three models, or …???

i appreciate any help…  
thanks.

harper

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 3, 2006, 4:29pm UTC](https://www.ruby-forum.com/t/help/96914/2 "2006-07-03T16:29:29Z")

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harper wrote:

> Hi,

> in MyController i have an action that selects rows from M1 with an  
> :include =\> ‘M2s’ and that changes the sql output to “outer left  
> join…etc” which is great. . . but when i want to add a :conditions  
> clause, i find that it doesn’t add the conditon correctly into the outer  
> left join sql command, and it ends up giving me an sql syntax error!  
> If i try to use the :conditions clause alone (without :include) , i get  
> no error, which is great.  
> 🙂

Hi Harper. This all sounds incredibly complicated, and perhaps there’s  
something I’m missing in your question that requires that complexity,  
but here’s the simple case.

Where foo has\_and\_belongs\_to\_many :bars you create the bollowing tables:

foos (id, name, etc)  
bars (id, description, etc)  
bars\_foos (bar\_id, foo\_id)

Here, bars\_foos is the ‘join table’ which implements the habtm  
relationship.

from a given foo, you can ask for bars.first.description, or iterate  
across it like

bars.each{ |b| b.description }

That all works out of the box. All you need is the habtm declaration  
and the tables…no magic sql.

Since you have three entity table and two habmt relationships, you need  
to join tables. I’ll call your models Alpha, Beta and Gamma.

alphas (id, blah, blah )  
betas (id, blah, blah )  
gammas (id, blah, blah )

alphas\_betas(alpha\_id, beta\_id)  
betas\_gammas(beta\_id, gamma\_id)

And declare the habtms in the appropriate places.

Does this help at all ?

Alan

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 3, 2006, 6:13pm UTC](https://www.ruby-forum.com/t/help/96914/3 "2006-07-03T18:13:53Z")

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Hi Alan,

first of all firsts, thank you for your detailed answer and a piece of  
your time; it’s greatly appreciated.  
so, the deal is that i have done all of the above, and the habtam  
relashinship works great between the three models. i can append a alpha  
into the beta.alphas array, and a beta into the gama.betas array, and  
yatta yatta. everything works like a charm.  
the problem i am having is trying to select Alpah.find(:all, :include =\>  
betas, :conditions =\> beta\_id in (1,3,a,b,5…) AND ##this is the  
important part where i fail### title LIKE ?", #{beta.title})  
for some very annoying reason, i can’t use a condition statement,  
becuase the outputted sql command is not in the right clause (a ‘where  
blah = blah’ and ‘outer left join’ habtam relashinships).  
i found this a sec ago:

“…The problem that eager loading does not honor conditions and  
ordering  
is a long known one, but dealing with it seems  
extremely convoluted as I see it (to do it properly you really need a  
PROPER database that doesn’t die on you when  
you do nested SELECTs).” (= i.e, there’s no way to combine a habtam  
relashinship ‘find’ statement with a ‘conditions’. don’t know why, but  
that’s the deal)

do you know any other way to combine a :conditons and an :include  
statemnt under the same ‘find’ action(when under a habtam relashinship)?  
maybe i got it all wrong, and there is some stupid mistake. if i was  
told clear-cut, that there shouldn’t be a problem, i’d go and try to do  
it again , however i can’t find anyone who will give me a clear answer;  
and if i CAN’T combine the two statements together, well, how do i ?

again, your help is much much much,  
much, appreciated.

thanks.  
harper

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 4, 2006, 11:50am UTC](https://www.ruby-forum.com/t/help/96914/4 "2006-07-04T11:50:35Z")

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harper wrote:

“Also have in mind that since the eager loading is pulling from multiple  
tables, youâ??ll have to disambiguate any column references in both  
conditions and orders. So :order =\> “posts.id DESC” will work while  
:order =\> “id DESC” will not. This may require that you alter the :order  
and :conditions on the association definitions themselves.”

perhaps you need to specify the tables in the :conditions ?

:conditions =\> “alphas.beta\_id in (1,3,a,b,5…) AND betas.title LIKE ?”,  
#{beta.title})"

A.  
p.s. why restrict beta on both id and title at the same time ? If you  
know the beta\_id, do you need the title ?  
p.p.s Any chance you could give us the real model names, it’ll sit  
easier in the brain.

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 4, 2006, 11:56am UTC](https://www.ruby-forum.com/t/help/96914/5 "2006-07-04T11:56:47Z")

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I see you resolved this in another thread 🙂

Alan

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 4, 2006, 11:36am UTC](https://www.ruby-forum.com/t/help/96914/6 "2006-07-04T11:36:24Z")

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harper wrote:

Hi Harper,

> first of all firsts, thank you for your detailed answer and a piece of  
> your time; it’s greatly appreciated.

Absolutely no problem.

> do you know any other way to combine a :conditons and an :include  
> statemnt under the same ‘find’ action(when under a habtam relashinship)?  
> maybe i got it all wrong, and there is some stupid mistake. if i was  
> told clear-cut, that there shouldn’t be a problem, i’d go and try to do  
> it again , however i can’t find anyone who will give me a clear answer;  
> and if i CAN’T combine the two statements together, well, how do i ?

I’m afraid I’m out of my depth. My Rails knowledge is broad but shallow  
🙂 I’ll try and do a bit of digging in parallel.

At the risk of appearing to dodge the question, do you _need_ the eager  
loading ? Have you seen a performance problem ? Hopefully it doesn’t  
look too much like dodging the question, as I started with an honest “I  
have no idea” 🙂

A.

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<div class="post-metadata">

**Author:** ![harper](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/b5ac83/32.png) [@harper](https://www.ruby-forum.com/u/harper)\
**Post date:** [July 4, 2006, 12:49pm UTC](https://www.ruby-forum.com/t/help/96914/7 "2006-07-04T12:49:14Z")

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yea…  
i totaly didn’t follow what was going on in this thread…although now  
that i’ve found out, you should see the smile behind the computer  
screen.  
thanks for the concern!

harp