Hi everyone,
I have the following basic rules:
Subject has many elements
Element has many subjects
Element has many knowledges which are either enabled or required
Element has many skills which are either enabled or required
I have designed the schema to have 6 tables, Subjects, Elements,
PriorKnowledge, PriorSkills, EnabledKnowledge and EnabledSkills.
Now to my problem. I am trying to build a page that will display all
this information. It will display a subject and all its elements, and
all of the elements prior and enabled, knowledges and skills.
The thought that I had was to use has_many :through relationships, but I
don''t know how to handle both prior and enabled cases.
My next thought was to use a sql query to select the knowledge and skill
elements required and save them as class variables in elements. However
I don''t know how to get the ID of the element i am working with.
This is the SQL query that does the job:
select description from knowledges where id in (select
knowledges_id from prior_knowledges where elements_id = 1);
I had this line in the element.rb file:
@@pk = Knowlegde.find_by_sql("select description from knowledges
where id in (select knowledges_id from prior_knowledges where
elements_id = " + id.to_s + ");")
But i kept getting a empty array but executing the same command in SQL
works, and executing the command manually in the console also works.
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On Jul 13, 6:03 am, Adrian Zatta <li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> Hi everyone, > I have the following basic rules: > Subject has many elements > Element has many subjects > Element has many knowledges which are either enabled or required > Element has many skills which are either enabled or required > > I have designed the schema to have 6 tables, Subjects, Elements, > PriorKnowledge, PriorSkills, EnabledKnowledge and EnabledSkills. >> Now to my problem. I am trying to build a page that will display all > this information. It will display a subject and all its elements, and > all of the elements prior and enabled, knowledges and skills. > > The thought that I had was to use has_many :through relationships, but I > don''t know how to handle both prior and enabled cases.Is PriorKnowledge the join table between elements and EnabledKnowledges? If so has_many :through sounds like the right thing - what did you try that didn''t work ? Fred -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On 13 July 2010 06:03, Adrian Zatta <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> Hi everyone, > I have the following basic rules: > Subject has many elements > Element has many subjects > Element has many knowledges which are either enabled or required > Element has many skills which are either enabled or required > > I have designed the schema to have 6 tables, Subjects, Elements, > PriorKnowledge, PriorSkills, EnabledKnowledge and EnabledSkills.You talked about required earlier, is that the same as prior? Is there a good reason why you don''t just put PriorKnowledge and EnabledKnowledge in the same class and table with a boolean to indicate which?> > Now to my problem. I am trying to build a page that will display all > this information. It will display a subject and all its elements, and > all of the elements prior and enabled, knowledges and skills. > > The thought that I had was to use has_many :through relationships, but I > don''t know how to handle both prior and enabled cases.I am obviously missing something, why can''t you just say @element.prior_knowledge and @element.enabled_logic> > My next thought was to use a sql query to select the knowledge and skill > elements required and save them as class variables in elements. However > I don''t know how to get the ID of the element i am working with. > > This is the SQL query that does the job: > select description from knowledges where id in (select > knowledges_id from prior_knowledges where elements_id = 1);Now you seem to have a ''knowledges'' table which you have not mentioned before. Colin> > I had this line in the element.rb file: > @@pk = Knowlegde.find_by_sql("select description from knowledges > where id in (select knowledges_id from prior_knowledges where > elements_id = " + id.to_s + ");") > But i kept getting a empty array but executing the same command in SQL > works, and executing the command manually in the console also works.-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Yeah, Sorry, I also have a Knowledge and Skills table which i forgot to add to my initial post. And yes, prior is the same as required. I think what Colin suggested about using a boolean may actually work quite well. The problem i was having using the :through was that in writing, "has_many knowledges, :through prior_knowledges", i would also have, "has_many knowledges, :through enabled_knowledges". But using a boolean should solve that problem. Thanks very much for your suggestions, and sorry about my convoluted explanations. Colin Law wrote:> On 13 July 2010 06:03, Adrian Zatta <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote: >> Hi everyone, >> I have the following basic rules: >> �Subject has many elements >> �Element has many subjects >> �Element has many knowledges which are either enabled or required >> �Element has many skills which are either enabled or required >> >> I have designed the schema to have 6 tables, Subjects, Elements, >> PriorKnowledge, PriorSkills, EnabledKnowledge and EnabledSkills. > > You talked about required earlier, is that the same as prior? > > Is there a good reason why you don''t just put PriorKnowledge and > EnabledKnowledge in the same class and table with a boolean to > indicate which? > >> >> Now to my problem. I am trying to build a page that will display all >> this information. It will display a subject and all its elements, and >> all of the elements prior and enabled, knowledges and skills. >> >> The thought that I had was to use has_many :through relationships, but I >> don''t know how to handle both prior and enabled cases. > > I am obviously missing something, why can''t you just say > @element.prior_knowledge > and > @element.enabled_logic > >> >> My next thought was to use a sql query to select the knowledge and skill >> elements required and save them as class variables in elements. However >> I don''t know how to get the ID of the element i am working with. >> >> This is the SQL query that does the job: >> � � � select description from knowledges where id in (select >> knowledges_id from prior_knowledges where elements_id = 1); > > Now you seem to have a ''knowledges'' table which you have not mentioned > before. > > Colin-- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.