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<section id="using-sqlalchemy">
<h1>Using SQLAlchemy<a class="headerlink" href="#using-sqlalchemy" title="Link to this heading"></a></h1>
<p>Most real web applications need a database. This guide shows how to
integrate <a class="reference external" href="https://www.sqlalchemy.org/">SQLAlchemy</a> with Responder,
using async support and the lifespan pattern for connection management.</p>
<p>SQLAlchemy is the most popular Python database toolkit. It gives you an
ORM (Object-Relational Mapper) for working with databases using Python
classes instead of raw SQL, plus a powerful query builder for when you
need fine-grained control.</p>
<section id="installation">
<h2>Installation<a class="headerlink" href="#installation" title="Link to this heading"></a></h2>
<p>Install SQLAlchemy with async support and an async database driver.
We’ll use SQLite for simplicity, but the pattern works with PostgreSQL,
MySQL, and any other database SQLAlchemy supports:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ uv pip install &#39;sqlalchemy[asyncio]&#39; aiosqlite
</pre></div>
</div>
</section>
<section id="define-your-models">
<h2>Define Your Models<a class="headerlink" href="#define-your-models" title="Link to this heading"></a></h2>
<p>SQLAlchemy models map Python classes to database tables. Each attribute
becomes a column:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># models.py</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">String</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.orm</span><span class="w"> </span><span class="kn">import</span> <span class="n">DeclarativeBase</span><span class="p">,</span> <span class="n">Mapped</span><span class="p">,</span> <span class="n">mapped_column</span>
<span class="k">class</span><span class="w"> </span><span class="nc">Base</span><span class="p">(</span><span class="n">DeclarativeBase</span><span class="p">):</span>
<span class="k">pass</span>
<span class="k">class</span><span class="w"> </span><span class="nc">Book</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">&quot;books&quot;</span>
<span class="nb">id</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">int</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</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">autoincrement</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<span class="n">title</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">str</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</span><span class="p">(</span><span class="n">String</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">author</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">str</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</span><span class="p">(</span><span class="n">String</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">year</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">int</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</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">isbn</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">str</span> <span class="o">|</span> <span class="kc">None</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</span><span class="p">(</span><span class="n">String</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</pre></div>
</div>
<p>This uses SQLAlchemy 2.0’s <code class="docutils literal notranslate"><span class="pre">Mapped</span></code> type annotations and
<code class="docutils literal notranslate"><span class="pre">mapped_column()</span></code>, which give you type checker support and cleaner
syntax than the older <code class="docutils literal notranslate"><span class="pre">Column()</span></code> style. Each model class corresponds
to a table, and each <code class="docutils literal notranslate"><span class="pre">mapped_column()</span></code> corresponds to a column.</p>
</section>
<section id="database-setup">
<h2>Database Setup<a class="headerlink" href="#database-setup" title="Link to this heading"></a></h2>
<p>Create the async engine and session factory. The <em>engine</em> manages
the connection pool. The <em>session</em> is your unit of work — you use it to
query and modify data within a transaction:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># database.py</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.ext.asyncio</span><span class="w"> </span><span class="kn">import</span> <span class="n">create_async_engine</span><span class="p">,</span> <span class="n">async_sessionmaker</span>
<span class="n">DATABASE_URL</span> <span class="o">=</span> <span class="s2">&quot;sqlite+aiosqlite:///./books.db&quot;</span>
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_async_engine</span><span class="p">(</span><span class="n">DATABASE_URL</span><span class="p">,</span> <span class="n">echo</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<span class="n">async_session</span> <span class="o">=</span> <span class="n">async_sessionmaker</span><span class="p">(</span><span class="n">engine</span><span class="p">,</span> <span class="n">expire_on_commit</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">echo=True</span></code> flag prints all SQL queries to the console — very
helpful during development, but you’ll want to disable it in production.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">expire_on_commit=False</span></code> flag keeps model attributes accessible
after a commit, which is convenient for returning created objects in
API responses.</p>
</section>
<section id="lifespan-for-startup-and-shutdown">
<h2>Lifespan for Startup and Shutdown<a class="headerlink" href="#lifespan-for-startup-and-shutdown" title="Link to this heading"></a></h2>
<p>Use Responder’s lifespan context manager to create the database tables
on startup and dispose of connections on shutdown:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># app.py</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">contextlib</span><span class="w"> </span><span class="kn">import</span> <span class="n">asynccontextmanager</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">responder</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">database</span><span class="w"> </span><span class="kn">import</span> <span class="n">engine</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">models</span><span class="w"> </span><span class="kn">import</span> <span class="n">Base</span>
<span class="nd">@asynccontextmanager</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">lifespan</span><span class="p">(</span><span class="n">app</span><span class="p">):</span>
<span class="c1"># Startup: create tables</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">engine</span><span class="o">.</span><span class="n">begin</span><span class="p">()</span> <span class="k">as</span> <span class="n">conn</span><span class="p">:</span>
<span class="k">await</span> <span class="n">conn</span><span class="o">.</span><span class="n">run_sync</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="k">yield</span>
<span class="c1"># Shutdown: close all connections</span>
<span class="k">await</span> <span class="n">engine</span><span class="o">.</span><span class="n">dispose</span><span class="p">()</span>
<span class="n">api</span> <span class="o">=</span> <span class="n">responder</span><span class="o">.</span><span class="n">API</span><span class="p">(</span><span class="n">lifespan</span><span class="o">=</span><span class="n">lifespan</span><span class="p">)</span>
</pre></div>
</div>
<p>This is the proper way to manage database connections in an async
application. The lifespan context manager ensures that:</p>
<ol class="arabic simple">
<li><p>Tables are created before the first request</p></li>
<li><p>The connection pool is properly closed when the server shuts down</p></li>
<li><p>If table creation fails, the server won’t start</p></li>
</ol>
</section>
<section id="crud-endpoints">
<h2>CRUD Endpoints<a class="headerlink" href="#crud-endpoints" title="Link to this heading"></a></h2>
<p>Now let’s build the API endpoints. Each one opens a database session,
does its work, and commits or rolls back:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">pydantic</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseModel</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">select</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">database</span><span class="w"> </span><span class="kn">import</span> <span class="n">async_session</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">models</span><span class="w"> </span><span class="kn">import</span> <span class="n">Book</span>
<span class="c1"># Pydantic models for request/response validation</span>
<span class="k">class</span><span class="w"> </span><span class="nc">BookIn</span><span class="p">(</span><span class="n">BaseModel</span><span class="p">):</span>
<span class="n">title</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">author</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">year</span><span class="p">:</span> <span class="nb">int</span>
<span class="n">isbn</span><span class="p">:</span> <span class="nb">str</span> <span class="o">|</span> <span class="kc">None</span> <span class="o">=</span> <span class="kc">None</span>
<span class="k">class</span><span class="w"> </span><span class="nc">BookOut</span><span class="p">(</span><span class="n">BaseModel</span><span class="p">):</span>
<span class="nb">id</span><span class="p">:</span> <span class="nb">int</span>
<span class="n">title</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">author</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">year</span><span class="p">:</span> <span class="nb">int</span>
<span class="n">isbn</span><span class="p">:</span> <span class="nb">str</span> <span class="o">|</span> <span class="kc">None</span> <span class="o">=</span> <span class="kc">None</span>
<span class="k">class</span><span class="w"> </span><span class="nc">Config</span><span class="p">:</span>
<span class="n">from_attributes</span> <span class="o">=</span> <span class="kc">True</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">from_attributes</span> <span class="pre">=</span> <span class="pre">True</span></code> config tells Pydantic to read data from
SQLAlchemy model attributes (not just dicts). This lets you pass a
SQLAlchemy <code class="docutils literal notranslate"><span class="pre">Book</span></code> object directly to <code class="docutils literal notranslate"><span class="pre">BookOut</span></code>.</p>
<p><strong>List all books</strong>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nd">@api</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">&quot;/books&quot;</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;GET&quot;</span><span class="p">])</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">list_books</span><span class="p">(</span><span class="n">req</span><span class="p">,</span> <span class="n">resp</span><span class="p">):</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">async_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="n">select</span><span class="p">(</span><span class="n">Book</span><span class="p">))</span>
<span class="n">books</span> <span class="o">=</span> <span class="n">result</span><span class="o">.</span><span class="n">scalars</span><span class="p">()</span><span class="o">.</span><span class="n">all</span><span class="p">()</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="p">[</span><span class="n">BookOut</span><span class="o">.</span><span class="n">model_validate</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="o">.</span><span class="n">model_dump</span><span class="p">()</span> <span class="k">for</span> <span class="n">b</span> <span class="ow">in</span> <span class="n">books</span><span class="p">]</span>
</pre></div>
</div>
<p><strong>Create a book</strong>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nd">@api</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">&quot;/books&quot;</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;POST&quot;</span><span class="p">],</span> <span class="n">check_existing</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">request_model</span><span class="o">=</span><span class="n">BookIn</span><span class="p">,</span> <span class="n">response_model</span><span class="o">=</span><span class="n">BookOut</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_book</span><span class="p">(</span><span class="n">req</span><span class="p">,</span> <span class="n">resp</span><span class="p">):</span>
<span class="n">data</span> <span class="o">=</span> <span class="k">await</span> <span class="n">req</span><span class="o">.</span><span class="n">media</span><span class="p">()</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">async_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<span class="n">book</span> <span class="o">=</span> <span class="n">Book</span><span class="p">(</span><span class="o">**</span><span class="n">data</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">book</span><span class="p">)</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">refresh</span><span class="p">(</span><span class="n">book</span><span class="p">)</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="n">BookOut</span><span class="o">.</span><span class="n">model_validate</span><span class="p">(</span><span class="n">book</span><span class="p">)</span><span class="o">.</span><span class="n">model_dump</span><span class="p">()</span>
<span class="n">resp</span><span class="o">.</span><span class="n">status_code</span> <span class="o">=</span> <span class="mi">201</span>
</pre></div>
</div>
<p><strong>Get a single book</strong>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nd">@api</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">&quot;/books/{book_id:int}&quot;</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;GET&quot;</span><span class="p">])</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">get_book</span><span class="p">(</span><span class="n">req</span><span class="p">,</span> <span class="n">resp</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">book_id</span><span class="p">):</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">async_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<span class="n">book</span> <span class="o">=</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">Book</span><span class="p">,</span> <span class="n">book_id</span><span class="p">)</span>
<span class="k">if</span> <span class="n">book</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">resp</span><span class="o">.</span><span class="n">status_code</span> <span class="o">=</span> <span class="mi">404</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="p">{</span><span class="s2">&quot;error&quot;</span><span class="p">:</span> <span class="s2">&quot;Book not found&quot;</span><span class="p">}</span>
<span class="k">return</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="n">BookOut</span><span class="o">.</span><span class="n">model_validate</span><span class="p">(</span><span class="n">book</span><span class="p">)</span><span class="o">.</span><span class="n">model_dump</span><span class="p">()</span>
</pre></div>
</div>
<p><strong>Update a book</strong>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nd">@api</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">&quot;/books/{book_id:int}&quot;</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;PUT&quot;</span><span class="p">],</span> <span class="n">check_existing</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">request_model</span><span class="o">=</span><span class="n">BookIn</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">update_book</span><span class="p">(</span><span class="n">req</span><span class="p">,</span> <span class="n">resp</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">book_id</span><span class="p">):</span>
<span class="n">data</span> <span class="o">=</span> <span class="k">await</span> <span class="n">req</span><span class="o">.</span><span class="n">media</span><span class="p">()</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">async_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<span class="n">book</span> <span class="o">=</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">Book</span><span class="p">,</span> <span class="n">book_id</span><span class="p">)</span>
<span class="k">if</span> <span class="n">book</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">resp</span><span class="o">.</span><span class="n">status_code</span> <span class="o">=</span> <span class="mi">404</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="p">{</span><span class="s2">&quot;error&quot;</span><span class="p">:</span> <span class="s2">&quot;Book not found&quot;</span><span class="p">}</span>
<span class="k">return</span>
<span class="k">for</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">data</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="nb">setattr</span><span class="p">(</span><span class="n">book</span><span class="p">,</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">refresh</span><span class="p">(</span><span class="n">book</span><span class="p">)</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="n">BookOut</span><span class="o">.</span><span class="n">model_validate</span><span class="p">(</span><span class="n">book</span><span class="p">)</span><span class="o">.</span><span class="n">model_dump</span><span class="p">()</span>
</pre></div>
</div>
<p><strong>Delete a book</strong>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nd">@api</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">&quot;/books/{book_id:int}&quot;</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;DELETE&quot;</span><span class="p">],</span> <span class="n">check_existing</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">delete_book</span><span class="p">(</span><span class="n">req</span><span class="p">,</span> <span class="n">resp</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">book_id</span><span class="p">):</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">async_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<span class="n">book</span> <span class="o">=</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">Book</span><span class="p">,</span> <span class="n">book_id</span><span class="p">)</span>
<span class="k">if</span> <span class="n">book</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">resp</span><span class="o">.</span><span class="n">status_code</span> <span class="o">=</span> <span class="mi">404</span>
<span class="n">resp</span><span class="o">.</span><span class="n">media</span> <span class="o">=</span> <span class="p">{</span><span class="s2">&quot;error&quot;</span><span class="p">:</span> <span class="s2">&quot;Book not found&quot;</span><span class="p">}</span>
<span class="k">return</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">delete</span><span class="p">(</span><span class="n">book</span><span class="p">)</span>
<span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="n">resp</span><span class="o">.</span><span class="n">status_code</span> <span class="o">=</span> <span class="mi">204</span>
</pre></div>
</div>
</section>
<section id="run-it">
<h2>Run It<a class="headerlink" href="#run-it" title="Link to this heading"></a></h2>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>
<span class="n">api</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
<p>Start the server and you’ll see SQLAlchemy’s SQL echo in the console.
The SQLite database file <code class="docutils literal notranslate"><span class="pre">books.db</span></code> is created automatically on first
startup.</p>
</section>
<section id="using-postgresql">
<h2>Using PostgreSQL<a class="headerlink" href="#using-postgresql" title="Link to this heading"></a></h2>
<p>To switch to PostgreSQL, just change the connection URL and driver:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ uv pip install asyncpg
</pre></div>
</div>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">DATABASE_URL</span> <span class="o">=</span> <span class="s2">&quot;postgresql+asyncpg://user:pass@localhost/mydb&quot;</span>
</pre></div>
</div>
<p>Everything else stays the same. SQLAlchemy abstracts the database
differences so your application code doesn’t need to change.</p>
</section>
<section id="tips">
<h2>Tips<a class="headerlink" href="#tips" title="Link to this heading"></a></h2>
<ul class="simple">
<li><p>Use <code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">with</span> <span class="pre">async_session()</span> <span class="pre">as</span> <span class="pre">session</span></code> for every request.
Don’t share sessions across requests — each request should get its
own session and transaction.</p></li>
<li><p>For complex queries, use SQLAlchemy’s <code class="docutils literal notranslate"><span class="pre">select()</span></code> with <code class="docutils literal notranslate"><span class="pre">.where()</span></code>,
<code class="docutils literal notranslate"><span class="pre">.order_by()</span></code>, <code class="docutils literal notranslate"><span class="pre">.limit()</span></code>, and <code class="docutils literal notranslate"><span class="pre">.offset()</span></code> — it composes
naturally.</p></li>
<li><p>In production, use connection pooling (SQLAlchemy does this by
default) and set pool size limits appropriate for your database.</p></li>
<li><p>Consider <a class="reference external" href="https://alembic.sqlalchemy.org/">Alembic</a> for database
migrations — it tracks schema changes over time so you can evolve
your database without losing data.</p></li>
</ul>
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<h3><a href="index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Using SQLAlchemy</a><ul>
<li><a class="reference internal" href="#installation">Installation</a></li>
<li><a class="reference internal" href="#define-your-models">Define Your Models</a></li>
<li><a class="reference internal" href="#database-setup">Database Setup</a></li>
<li><a class="reference internal" href="#lifespan-for-startup-and-shutdown">Lifespan for Startup and Shutdown</a></li>
<li><a class="reference internal" href="#crud-endpoints">CRUD Endpoints</a></li>
<li><a class="reference internal" href="#run-it">Run It</a></li>
<li><a class="reference internal" href="#using-postgresql">Using PostgreSQL</a></li>
<li><a class="reference internal" href="#tips">Tips</a></li>
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