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[Mysqli_Result :: fetch_fields Wie verwendet man mySQLI_Fetch_assoc, um komplexe Abfragen zu implementieren?

gitbox 2025-08-16 
<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// Dies hängt nicht mit dem Inhalt des Artikels zusammenPHPCodeabschnitt，Kann jeder Initialisierungs- oder Konfigurationscode sein</span></span><span>
</span><span><span class="hljs-variable">$servername</span></span><span> = </span><span><span class="hljs-string">"localhost"</span></span><span>;
</span><span><span class="hljs-variable">$username</span></span><span> = </span><span><span class="hljs-string">"root"</span></span><span>;
</span><span><span class="hljs-variable">$password</span></span><span> = </span><span><span class="hljs-string">""</span></span><span>;
</span><span><span class="hljs-variable">$dbname</span></span><span> = </span><span><span class="hljs-string">"test_db"</span></span><span>;

</span><span><span class="hljs-variable">$conn</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title function_ invoke__">mysqli</span></span><span>(</span><span><span class="hljs-variable">$servername</span></span><span>, </span><span><span class="hljs-variable">$username</span></span><span>, </span><span><span class="hljs-variable">$password</span></span><span>, </span><span><span class="hljs-variable">$dbname</span></span><span>);
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$conn</span></span><span>-&gt;connect_error) {
    </span><span><span class="hljs-keyword">die</span></span><span>(</span><span><span class="hljs-string">"Verbindung ist fehlgeschlagen: "</span></span><span> . </span><span><span class="hljs-variable">$conn</span></span><span>-&gt;connect_error);
}

</span><span><span class="hljs-variable">$query</span></span><span> = </span><span><span class="hljs-string">"SELECT users.id, users.name, orders.order_date, orders.amount FROM users LEFT JOIN orders ON users.id = orders.user_id"</span></span><span>;
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$conn</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">query</span></span><span>(</span><span><span class="hljs-variable">$query</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>

&lt;hr&gt;

</span><span><span class="hljs-meta">&lt;?php</span></span><span>
<span class="hljs-comment">/*
 * mysqli_result::fetch_fields() Und mysqli_fetch_assoc() Gemeinsame Verwendung
 * Wird verwendet, um die dynamische Verarbeitung komplexer Abfrageergebnisse zu implementieren
 *
 * Komplexe Abfrage，Es kann viele Feldnamen geben，Und es gibt Duplikate oder Alias，verwendenfetch_fieldsKann Feldmeta -Informationen erhalten，
 * Kombiniertfetch_assocDaten können Zeile für Zeile für Zeile im assoziativen Array gelesen werden，Erzielen Sie flexiblere Datenoperationen。
 */</span>

</span><span><span class="hljs-comment">// 1. Erhalten Sie Feldinformationen</span></span><span>
</span><span><span class="hljs-variable">$fields</span></span><span> = </span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetch_fields</span></span><span>();

</span><span><span class="hljs-comment">// 2. Drucken Sie alle Feldnamen（Demo -Nutzung）</span></span><span>
</span><span><span class="hljs-variable">$fieldNames</span></span><span> = [];
</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$fields</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$field</span></span><span>) {
    </span><span><span class="hljs-variable">$fieldNames</span></span><span>[] = </span><span><span class="hljs-variable">$field</span></span><span>-&gt;name;
}
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Queryfelder haben: "</span></span><span> . </span><span><span class="hljs-title function_ invoke__">implode</span></span><span>(</span><span><span class="hljs-string">", "</span></span><span>, </span><span><span class="hljs-variable">$fieldNames</span></span><span>) . </span><span><span class="hljs-string">"&lt;br&gt;&lt;br&gt;"</span></span><span>;

</span><span><span class="hljs-comment">// 3. Holen Sie sich die Datenzeile nach Zeile und organisieren Sie Arrays mit Feldnamen als Schlüssel</span></span><span>
</span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-variable">$row</span></span><span> = </span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetch_assoc</span></span><span>()) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"BenutzerID: "</span></span><span> . </span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>] . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Benutzer名: "</span></span><span> . </span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'name'</span></span><span>] . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Bestelldatum: "</span></span><span> . (</span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'order_date'</span></span><span>] ?? </span><span><span class="hljs-string">'Keine Bestellung'</span></span><span>) . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Bestellmenge: "</span></span><span> . (</span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'amount'</span></span><span>] ?? </span><span><span class="hljs-string">'Keine Menge'</span></span><span>) . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"&lt;hr&gt;"</span></span><span>;
}

</span><span><span class="hljs-comment">// 4. Schließen Sie die Verbindung</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">free</span></span><span>();
</span><span><span class="hljs-variable">$conn</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">close</span></span><span>();
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>
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