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<div class="section" id="database-metadata">
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<h1>Database Metadata<a class="headerlink" href="#database-metadata" title="Permalink to this headline">¶</a></h1>
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<div class="contents local topic" id="contents">
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<ul class="simple">
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<li><a class="reference internal" href="#table-metadata" id="id1">Table MetaData</a><ul>
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<li><a class="reference internal" href="#list-the-tables-in-your-database" id="id2">List the Tables in Your Database</a></li>
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<li><a class="reference internal" href="#determine-if-a-table-exists" id="id3">Determine If a Table Exists</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#field-metadata" id="id4">Field MetaData</a><ul>
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<li><a class="reference internal" href="#list-the-fields-in-a-table" id="id5">List the Fields in a Table</a></li>
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<li><a class="reference internal" href="#determine-if-a-field-is-present-in-a-table" id="id6">Determine If a Field is Present in a Table</a></li>
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<li><a class="reference internal" href="#retrieve-field-metadata" id="id7">Retrieve Field Metadata</a></li>
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<li><a class="reference internal" href="#list-the-indexes-in-a-table" id="id8">List the Indexes in a Table</a></li>
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</ul>
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</li>
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</ul>
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</div>
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<div class="section" id="table-metadata">
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<h2><a class="toc-backref" href="#id1">Table MetaData</a><a class="headerlink" href="#table-metadata" title="Permalink to this headline">¶</a></h2>
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<p>These functions let you fetch table information.</p>
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<div class="section" id="list-the-tables-in-your-database">
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<h3><a class="toc-backref" href="#id2">List the Tables in Your Database</a><a class="headerlink" href="#list-the-tables-in-your-database" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->listTables();</strong></p>
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<p>Returns an array containing the names of all the tables in the database
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you are currently connected to. Example:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$tables</span> <span class="o">=</span> <span class="nv">$db</span><span class="o">-></span><span class="na">listTables</span><span class="p">();</span>
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<span class="k">foreach</span> <span class="p">(</span><span class="nv">$tables</span> <span class="k">as</span> <span class="nv">$table</span><span class="p">)</span>
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<span class="p">{</span>
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<span class="k">echo</span> <span class="nv">$table</span><span class="p">;</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="determine-if-a-table-exists">
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<h3><a class="toc-backref" href="#id3">Determine If a Table Exists</a><a class="headerlink" href="#determine-if-a-table-exists" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->tableExists();</strong></p>
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<p>Sometimes it’s helpful to know whether a particular table exists before
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running an operation on it. Returns a boolean TRUE/FALSE. Usage example:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="p">(</span><span class="nv">$db</span><span class="o">-></span><span class="na">tableExists</span><span class="p">(</span><span class="s1">'table_name'</span><span class="p">))</span>
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<span class="p">{</span>
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<span class="c1">// some code...</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Replace <em>table_name</em> with the name of the table you are looking for.</p>
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</div>
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</div>
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</div>
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<div class="section" id="field-metadata">
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<h2><a class="toc-backref" href="#id4">Field MetaData</a><a class="headerlink" href="#field-metadata" title="Permalink to this headline">¶</a></h2>
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<div class="section" id="list-the-fields-in-a-table">
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<h3><a class="toc-backref" href="#id5">List the Fields in a Table</a><a class="headerlink" href="#list-the-fields-in-a-table" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->getFieldNames()</strong></p>
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<p>Returns an array containing the field names. This query can be called
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two ways:</p>
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<p>1. You can supply the table name and call it from the $db->
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object:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$fields</span> <span class="o">=</span> <span class="nv">$db</span><span class="o">-></span><span class="na">getFieldNames</span><span class="p">(</span><span class="s1">'table_name'</span><span class="p">);</span>
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<span class="k">foreach</span> <span class="p">(</span><span class="nv">$fields</span> <span class="k">as</span> <span class="nv">$field</span><span class="p">)</span>
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<span class="p">{</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="p">;</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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<p>2. You can gather the field names associated with any query you run by
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calling the function from your query result object:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$query</span> <span class="o">=</span> <span class="nv">$db</span><span class="o">-></span><span class="na">query</span><span class="p">(</span><span class="s1">'SELECT * FROM some_table'</span><span class="p">);</span>
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<span class="k">foreach</span> <span class="p">(</span><span class="nv">$query</span><span class="o">-></span><span class="na">getFieldNames</span><span class="p">()</span> <span class="k">as</span> <span class="nv">$field</span><span class="p">)</span>
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<span class="p">{</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="p">;</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="determine-if-a-field-is-present-in-a-table">
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<h3><a class="toc-backref" href="#id6">Determine If a Field is Present in a Table</a><a class="headerlink" href="#determine-if-a-field-is-present-in-a-table" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->fieldExists()</strong></p>
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<p>Sometimes it’s helpful to know whether a particular field exists before
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performing an action. Returns a boolean TRUE/FALSE. Usage example:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="p">(</span><span class="nv">$db</span><span class="o">-></span><span class="na">fieldExists</span><span class="p">(</span><span class="s1">'field_name'</span><span class="p">,</span> <span class="s1">'table_name'</span><span class="p">))</span>
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<span class="p">{</span>
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<span class="c1">// some code...</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Replace <em>field_name</em> with the name of the column you are looking
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for, and replace <em>table_name</em> with the name of the table you are
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looking for.</p>
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</div>
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</div>
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<div class="section" id="retrieve-field-metadata">
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<h3><a class="toc-backref" href="#id7">Retrieve Field Metadata</a><a class="headerlink" href="#retrieve-field-metadata" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->getFieldData()</strong></p>
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<p>Returns an array of objects containing field information.</p>
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<p>Sometimes it’s helpful to gather the field names or other metadata, like
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the column type, max length, etc.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Not all databases provide meta-data.</p>
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</div>
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<p>Usage example:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$fields</span> <span class="o">=</span> <span class="nv">$db</span><span class="o">-></span><span class="na">getFieldData</span><span class="p">(</span><span class="s1">'table_name'</span><span class="p">);</span>
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<span class="k">foreach</span> <span class="p">(</span><span class="nv">$fields</span> <span class="k">as</span> <span class="nv">$field</span><span class="p">)</span>
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<span class="p">{</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="o">-></span><span class="na">name</span><span class="p">;</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="o">-></span><span class="na">type</span><span class="p">;</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="o">-></span><span class="na">max_length</span><span class="p">;</span>
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<span class="k">echo</span> <span class="nv">$field</span><span class="o">-></span><span class="na">primary_key</span><span class="p">;</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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<p>If you have run a query already you can use the result object instead of
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supplying the table name:</p>
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<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$query</span> <span class="o">=</span> <span class="nv">$db</span><span class="o">-></span><span class="na">query</span><span class="p">(</span><span class="s2">"YOUR QUERY"</span><span class="p">);</span>
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<span class="nv">$fields</span> <span class="o">=</span> <span class="nv">$query</span><span class="o">-></span><span class="na">fieldData</span><span class="p">();</span>
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</pre></div>
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</div>
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<p>The following data is available from this function if supported by your
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database:</p>
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<ul class="simple">
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<li>name - column name</li>
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<li>max_length - maximum length of the column</li>
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<li>primary_key - 1 if the column is a primary key</li>
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<li>type - the type of the column</li>
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</ul>
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</div>
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<div class="section" id="list-the-indexes-in-a-table">
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<h3><a class="toc-backref" href="#id8">List the Indexes in a Table</a><a class="headerlink" href="#list-the-indexes-in-a-table" title="Permalink to this headline">¶</a></h3>
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<p><strong>$db->getIndexData()</strong></p>
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<p>please write this, someone...</p>
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</div>
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© Copyright 2014-2018 British Columbia Institute of Technology.
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Last updated on Dec 15, 2018.
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