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POFetching values via foreign keys with DataMapper
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copied!<p>I have two tables, <code>nodes</code> and <code>terms</code>.</p> <p>The relevant fields in <code>nodes</code> are: <code>nid</code> (primary key) and <code>value</code><br /> In <code>terms</code>, they are: <code>value</code>, <code>tid</code>, and <code>nid</code>, where <code>value</code> and <code>tid</code> together are the primary key and <code>nid</code> is a foreign key referencing <code>nodes.nid</code>.</p> <p>I want to add records to <code>terms</code>. I have the <code>tid</code> and <code>nid</code>, and the <code>value</code> I want to pull from the corresponding <code>node</code> - e.g. look up the <code>value</code> for a given <code>nid</code> in <code>node</code> and then put that as the <code>value</code> in <code>terms</code>.</p> <p>A way to do this in SQL might be:</p> <pre><code>INSERT INTO terms(tid, nid, value) values(mytid, mynid, ( select value from nodes where nid=mynid )); </code></pre> <p>Could somebody help me do this with DataMapper?</p> <pre><code>class Node include DataMapper::Resource property :nid, Serial, :key => true property :value, Integer end class Term include DataMapper::Resource property :tid, Integer, :key => true # how do I define nid and value? end # and then what do I give to Term.new or Term.create and how? </code></pre> <p>If anyone could point me to a good tutorial of DataMapper as well, I'd appreciate it. I've been using their online docs, but I've found the situations I find myself in are rarely covered there.</p>

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