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Release: <span class="version-num">0.9.8</span> | Release Date: October 13, 2014
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<h1>SQLAlchemy 0.9 Documentation</h1>
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<h1>Source code for examples.association.basic_association</h1><div class="highlight"><pre>
<span class="sd">"""basic_association.py</span>
<span class="sd">illustrate a many-to-many relationship between an</span>
<span class="sd">"Order" and a collection of "Item" objects, associating a purchase price</span>
<span class="sd">with each via an association object called "OrderItem"</span>
<span class="sd">The association object pattern is a form of many-to-many which</span>
<span class="sd">associates additional data with each association between parent/child.</span>
<span class="sd">The example illustrates an "order", referencing a collection</span>
<span class="sd">of "items", with a particular price paid associated with each "item".</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">datetime</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="p">(</span><span class="n">create_engine</span><span class="p">,</span> <span class="n">MetaData</span><span class="p">,</span> <span class="n">Table</span><span class="p">,</span> <span class="n">Column</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span>
<span class="n">String</span><span class="p">,</span> <span class="n">DateTime</span><span class="p">,</span> <span class="n">Float</span><span class="p">,</span> <span class="n">ForeignKey</span><span class="p">,</span> <span class="n">and_</span><span class="p">)</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="kn">import</span> <span class="n">mapper</span><span class="p">,</span> <span class="n">relationship</span><span class="p">,</span> <span class="n">Session</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="kn">import</span> <span class="n">declarative_base</span>
<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">()</span>
<span class="k">class</span> <span class="nc">Order</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'order'</span>
<span class="n">order_id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">customer_name</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="mi">30</span><span class="p">),</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="n">order_date</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">DateTime</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="n">order_items</span> <span class="o">=</span> <span class="n">relationship</span><span class="p">(</span><span class="s">"OrderItem"</span><span class="p">,</span> <span class="n">cascade</span><span class="o">=</span><span class="s">"all, delete-orphan"</span><span class="p">,</span>
<span class="n">backref</span><span class="o">=</span><span class="s">'order'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">customer_name</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">customer_name</span> <span class="o">=</span> <span class="n">customer_name</span>
<span class="k">class</span> <span class="nc">Item</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'item'</span>
<span class="n">item_id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">description</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="mi">30</span><span class="p">),</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="n">price</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Float</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">description</span><span class="p">,</span> <span class="n">price</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">description</span> <span class="o">=</span> <span class="n">description</span>
<span class="bp">self</span><span class="o">.</span><span class="n">price</span> <span class="o">=</span> <span class="n">price</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">'Item(</span><span class="si">%r</span><span class="s">, </span><span class="si">%r</span><span class="s">)'</span> <span class="o">%</span> <span class="p">(</span>
<span class="bp">self</span><span class="o">.</span><span class="n">description</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">price</span>
<span class="p">)</span>
<span class="k">class</span> <span class="nc">OrderItem</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'orderitem'</span>
<span class="n">order_id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">ForeignKey</span><span class="p">(</span><span class="s">'order.order_id'</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">item_id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">ForeignKey</span><span class="p">(</span><span class="s">'item.item_id'</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">price</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Float</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">item</span><span class="p">,</span> <span class="n">price</span><span class="o">=</span><span class="bp">None</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">item</span> <span class="o">=</span> <span class="n">item</span>
<span class="bp">self</span><span class="o">.</span><span class="n">price</span> <span class="o">=</span> <span class="n">price</span> <span class="ow">or</span> <span class="n">item</span><span class="o">.</span><span class="n">price</span>
<span class="n">item</span> <span class="o">=</span> <span class="n">relationship</span><span class="p">(</span><span class="n">Item</span><span class="p">,</span> <span class="n">lazy</span><span class="o">=</span><span class="s">'joined'</span><span class="p">)</span>
<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">'__main__'</span><span class="p">:</span>
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">'sqlite://'</span><span class="p">)</span>
<span class="n">Base</span><span class="o">.</span><span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="n">session</span> <span class="o">=</span> <span class="n">Session</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="c"># create catalog</span>
<span class="n">tshirt</span><span class="p">,</span> <span class="n">mug</span><span class="p">,</span> <span class="n">hat</span><span class="p">,</span> <span class="n">crowbar</span> <span class="o">=</span> <span class="p">(</span>
<span class="n">Item</span><span class="p">(</span><span class="s">'SA T-Shirt'</span><span class="p">,</span> <span class="mf">10.99</span><span class="p">),</span>
<span class="n">Item</span><span class="p">(</span><span class="s">'SA Mug'</span><span class="p">,</span> <span class="mf">6.50</span><span class="p">),</span>
<span class="n">Item</span><span class="p">(</span><span class="s">'SA Hat'</span><span class="p">,</span> <span class="mf">8.99</span><span class="p">),</span>
<span class="n">Item</span><span class="p">(</span><span class="s">'MySQL Crowbar'</span><span class="p">,</span> <span class="mf">16.99</span><span class="p">)</span>
<span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">add_all</span><span class="p">([</span><span class="n">tshirt</span><span class="p">,</span> <span class="n">mug</span><span class="p">,</span> <span class="n">hat</span><span class="p">,</span> <span class="n">crowbar</span><span class="p">])</span>
<span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c"># create an order</span>
<span class="n">order</span> <span class="o">=</span> <span class="n">Order</span><span class="p">(</span><span class="s">'john smith'</span><span class="p">)</span>
<span class="c"># add three OrderItem associations to the Order and save</span>
<span class="n">order</span><span class="o">.</span><span class="n">order_items</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">OrderItem</span><span class="p">(</span><span class="n">mug</span><span class="p">))</span>
<span class="n">order</span><span class="o">.</span><span class="n">order_items</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">OrderItem</span><span class="p">(</span><span class="n">crowbar</span><span class="p">,</span> <span class="mf">10.99</span><span class="p">))</span>
<span class="n">order</span><span class="o">.</span><span class="n">order_items</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">OrderItem</span><span class="p">(</span><span class="n">hat</span><span class="p">))</span>
<span class="n">session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">order</span><span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c"># query the order, print items</span>
<span class="n">order</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Order</span><span class="p">)</span><span class="o">.</span><span class="n">filter_by</span><span class="p">(</span><span class="n">customer_name</span><span class="o">=</span><span class="s">'john smith'</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="k">print</span><span class="p">([(</span><span class="n">order_item</span><span class="o">.</span><span class="n">item</span><span class="o">.</span><span class="n">description</span><span class="p">,</span> <span class="n">order_item</span><span class="o">.</span><span class="n">price</span><span class="p">)</span>
<span class="k">for</span> <span class="n">order_item</span> <span class="ow">in</span> <span class="n">order</span><span class="o">.</span><span class="n">order_items</span><span class="p">])</span>
<span class="c"># print customers who bought 'MySQL Crowbar' on sale</span>
<span class="n">q</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Order</span><span class="p">)</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="s">'order_items'</span><span class="p">,</span> <span class="s">'item'</span><span class="p">)</span>
<span class="n">q</span> <span class="o">=</span> <span class="n">q</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">and_</span><span class="p">(</span><span class="n">Item</span><span class="o">.</span><span class="n">description</span> <span class="o">==</span> <span class="s">'MySQL Crowbar'</span><span class="p">,</span>
<span class="n">Item</span><span class="o">.</span><span class="n">price</span> <span class="o">></span> <span class="n">OrderItem</span><span class="o">.</span><span class="n">price</span><span class="p">))</span>
<span class="k">print</span><span class="p">([</span><span class="n">order</span><span class="o">.</span><span class="n">customer_name</span> <span class="k">for</span> <span class="n">order</span> <span class="ow">in</span> <span class="n">q</span><span class="p">])</span></pre></div>
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