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    <p>All <code>select_related</code> does, is eagerly fetch the fields declared as <code>ForeignKey</code> within your model. It attempts to avoid extra database calls, it doesn't magically give you access to extra fields.</p> <p>In your example, that means that accessing <code>partassembly.subpart</code> will not result in an extra database select, since it was eagerly fetched with the <code>PartAssembly.objects.filter()</code> call.</p> <p>Your data model seems to be incorrect, but we'll get to that in a minute. First, I'll show you how to access all the bits and pieces with your current data model.</p> <pre><code>{% for partassembly in subpart_list %} &lt;tr&gt; &lt;td&gt;{{ partassembly.item_no }}&lt;/td&gt; {% for subpart in partassembly.subpart.subpart_set %} # database hit &lt;td&gt;{{ subpart.subpart }}&lt;/td&gt; &lt;td&gt;{{ subpart.subpart.description }}&lt;/td&gt; # database hit &lt;td&gt;{{ subpart.subpart.rev }}&lt;/td&gt; &lt;td&gt;{{ subpart.qty }}&lt;/td&gt; &lt;td&gt;{{ subpart.subpart.isc }}&lt;/td&gt; {% endfor %} &lt;/tr&gt; </code></pre> <p>Unfortunately, you have no way of knowing how far you need to recurse. You can access the part within the original PartAssembly, and you can reach the set of PartAssemblys from that Part, but there is no easy way of reaching the PartAssembly set for all Parts within the first PartAssembly. Wow, that was a mouthful!</p> <p>Now, onto your data model.</p> <p>Say you have a Part called a "3mm screw". That sounds like it could be used for a number of different Assemblys (I'm intentionally not using the 'ies' plural form). So you have an Assembly called a Desk, and an Assembly called a Chair. Each uses many of these 3mm screws. You want to describe how to build a Desk.</p> <pre><code> desk = PartAssembly.objects.filter(id=assemblyid) part = desk.subpart # lets pretend this returns a 3mm screw subassemblies = part.subpart_set.all() for a in subassemblies: a.subpart.description # could be a Chair, or a Desk, or anything really! </code></pre> <p>This happens because a single instance of a 3mm Screw (or ANY part), is shared between all assemblies. You aren't truly replicating a ManyToMany table at all. Your datamodel is saying that a single Part can be used in many Assemblys.</p> <p>What I think you really want to say, is that an Assembly can be a part of another Assembly. Each Assembly as a number of Parts associated with its construction.</p> <pre><code>class Assembly(models.Model): parent = models.ForeignKey('self', null=True, blank=True, related_name='children') parts = models.ManyToManyField(Part) name = models.CharField(max_length=..) </code></pre> <p>Now, when you want to build a chair, you can do something like:</p> <pre><code>assembly = Assembly.objects.get(name='Chair') children = assembly.children.all() print assembly for part in assembly.parts: print part # now you iterate over the tree of children, printing their parts as you go </code></pre> <p>So, your Assembly model has now transformed into a Tree structure of other Assemblys, each containing their own set of Parts. Now that you can recognise this is a Tree structure, you can investigate how to represent this structure in a database within Django.</p> <p>Luckily, there exists a library that does exactly this. <a href="https://github.com/django-mptt/django-mptt/" rel="nofollow">django-mptt</a> exists to help you represent tree structures. It gives you methods for iterating over the entire tree, and describing each tree in your templates.</p> <p>I know I've probably helped cause you more work than you thought would be required, but I think this will truly help you.</p> <p>Best of luck.</p>
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    1. USJosh Smeaton
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    1. COThis is quite the answer! Unfortunatly I tend to post on here at the end of the day, when I can't figure it out on my own, but then all my files are still at work, and I can't try them out out home! haha. Thanks for the help, I'll check it out and probably accept it in the morning.
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    2. COI'm intentionally staying away from differentiating top assemblies from sub assemblies from parts etc. The way this app will be used requires that at any given time a specific subassembly may be called up and parts will not consistently be in the same tier for various assemblies. I'll check out the mptt library. And probably when my model doesn't work inevitably I'll come back to this post. This is (for now) a R&D type project so I'm not too afraid of falling on my face and having to try something new (read: no deadline!) thanks josh
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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