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<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../concept.html"><strong aria-hidden="true">2.</strong> Concept</a></li><li><a href="../query-language/introduction.html"><strong aria-hidden="true">3.</strong> The Query Language</a></li><li><ol class="section"><li><a href="../query-language/select.html" class="active"><strong aria-hidden="true">3.1.</strong> Selection</a></li><li><a href="../query-language/order.html"><strong aria-hidden="true">3.2.</strong> Ordering</a></li><li><a href="../query-language/filter.html"><strong aria-hidden="true">3.3.</strong> Filtering</a></li></ol></li><li><a href="../derive/introduction.html"><strong aria-hidden="true">4.</strong> The Toql Derive</a></li><li><ol class="section"><li><a href="../derive/mapping.html"><strong aria-hidden="true">4.1.</strong> Mapping</a></li><li><a href="../derive/optional-fields.html"><strong aria-hidden="true">4.2.</strong> Optional Fields</a></li><li><a href="../derive/joins.html"><strong aria-hidden="true">4.3.</strong> Joins</a></li><li><a href="../derive/merges.html"><strong aria-hidden="true">4.4.</strong> Merges</a></li><li><a href="../derive/indelup.html"><strong aria-hidden="true">4.5.</strong> Insert / Delete / Update</a></li><li><a href="../derive/reference.html"><strong aria-hidden="true">4.6.</strong> Reference</a></li></ol></li></ol>
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<h1 class="menu-title">Toql guide</h1>
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<a class="header" href="#selecting-fields" id="selecting-fields"><h1>Selecting fields</h1></a>
<p>Fields are selected if they are mentioned in the query.</p>
<ul>
<li>
<p>Names without underscore represent typically columns or expressions from the table the query is run against. <code>id, name, fullName, emailAddress</code></p>
</li>
<li>
<p>Fields with underscores are called <em>fields with a path</em>. They are mapped to a joined or a merged dependency. For a join relationship, the join will be added to the SQL statement if the field is selected. For a merge relationship a second SQL query must be run to query and merge the dependency. <code>book_id, book_title, book_createdBy_id</code></p>
</li>
<li>
<p>To use a field only for filtering, but not for selection hide it with a dot. <code>.age, .book_id</code></p>
</li>
</ul>
<a class="header" href="#example" id="example"><h4>Example</h4></a>
<pre><code>id, book_id, .age eq 50
</code></pre>
<p>is translated into (SQL Mapper must be told how to join)</p>
<pre><code>SELECT a.id, b.id, null FROM User a JOIN Book b ON (a.book_id = b.id) WHERE a.age > 50
</code></pre>
<a class="header" href="#wildcards" id="wildcards"><h2>Wildcards</h2></a>
<p>There are two wildcards to select multiple fields. They can neither be filtered nor ordered.</p>
<ul>
<li>
<p><strong>**</strong> selects all mapped fields (top level and dependencies). Useful for development.</p>
</li>
<li>
<p><strong>*</strong> selects all fields from the top level.</p>
</li>
<li>
<p><strong><em>path_</em>*</strong> selects all fields from <em>path</em>.</p>
</li>
</ul>
<p>Fields can be excluded from the wildcard by setting them to <code>ignore wildcard</code>.</p>
<a class="header" href="#example-1" id="example-1"><h4>Example</h4></a>
<p><code>id, age, book_id, .age eq 50</code></p>
<p>can be expressed as</p>
<p><code>*, book_*, .age eq 50</code></p>
<p>can be expressed as</p>
<p><code>**, .age eq 50</code></p>
<p>and is translation into</p>
<p><code>SELECT id, book_id, age FROM FROM User a JOIN Book b ON (a.book_id = b.id) WHERE a.age > 50</code></p>
<p><em>Note that the <code>age</code> field is selected with **</em>.</p>
<a class="header" href="#roles" id="roles"><h2>Roles</h2></a>
<p>Fields can require roles from the query. This is the permission system from Toql.
An error is raised, if a query selects a field that it's not allowed to. However if the query
selects with a wildcard, the field will just be ignored.</p>
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