<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title> examples.association.basic_association — SQLAlchemy 1.2 Documentation </title> <!-- begin iterate through site-imported + sphinx environment css_files --> <link rel="stylesheet" href="../../../_static/pygments.css" type="text/css" /> <link rel="stylesheet" href="../../../_static/docs.css" type="text/css" /> <link rel="stylesheet" href="../../../_static/changelog.css" type="text/css" /> <link rel="stylesheet" href="../../../_static/sphinx_paramlinks.css" type="text/css" /> <!-- end iterate through site-imported + sphinx environment css_files --> <!-- begin layout.mako headers --> <link rel="index" title="Index" href="../../../genindex.html" /> <link rel="search" title="Search" href="../../../search.html" /> <link rel="copyright" title="Copyright" href="../../../copyright.html" /> <link rel="top" title="SQLAlchemy 1.2 Documentation" href="../../../index.html" /> <link rel="up" title="Module code" href="../../index.html" /> <!-- end layout.mako headers --> </head> <body> <div id="docs-container"> <div id="docs-top-navigation-container" class="body-background"> <div id="docs-header"> <div id="docs-version-header"> Release: <span class="version-num">1.2.19</span> | Release Date: April 15, 2019 </div> <h1>SQLAlchemy 1.2 Documentation</h1> </div> </div> <div id="docs-body-container"> <div id="fixed-sidebar" class=""> <div id="index-nav"> <form class="search" action="../../../search.html" method="get"> <label> Search terms: <input type="text" placeholder="search..." name="q" size="12" /> </label> <input type="submit" value="Search" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p> <a href="../../../contents.html">Contents</a> | <a href="../../../genindex.html">Index</a> </p> </div> </div> <div id="docs-body" class="" > <h1>Source code for examples.association.basic_association</h1><div class="highlight"><pre> <span></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="k">import</span> <span class="n">datetime</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">and_</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Column</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">create_engine</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">DateTime</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Float</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">ForeignKey</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Integer</span> <span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">String</span> <span class="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="k">import</span> <span class="n">declarative_base</span> <span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">relationship</span> <span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">Session</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="s2">"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="kc">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="kc">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="kc">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="s2">"OrderItem"</span><span class="p">,</span> <span class="n">cascade</span><span class="o">=</span><span class="s2">"all, delete-orphan"</span><span class="p">,</span> <span class="n">backref</span><span class="o">=</span><span class="s2">"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="s2">"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="kc">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="kc">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="kc">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="s2">"Item(</span><span class="si">%r</span><span class="s2">, </span><span class="si">%r</span><span class="s2">)"</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="s2">"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="s2">"order.order_id"</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="kc">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="s2">"item.item_id"</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="kc">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="kc">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="kc">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="s2">"joined"</span><span class="p">)</span> <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__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="s2">"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="c1"># 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="s2">"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="s2">"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="s2">"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="s2">"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="c1"># create an order</span> <span class="n">order</span> <span class="o">=</span> <span class="n">Order</span><span class="p">(</span><span class="s2">"john smith"</span><span class="p">)</span> <span class="c1"># 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="c1"># 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="s2">"john smith"</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span> <span class="nb">print</span><span class="p">(</span> <span class="p">[</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="p">)</span> <span class="c1"># 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="s2">"order_items"</span><span class="p">,</span> <span class="s2">"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="s2">"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="p">)</span> <span class="nb">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> </div> </div> <div id="docs-bottom-navigation" class="docs-navigation-links"> <div id="docs-copyright"> © <a href="../../../copyright.html">Copyright</a> 2007-2019, the SQLAlchemy authors and contributors. 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