title: How can I concatenate QStrings?
body: <p>I have a problem with printing in Qt.</p>
  
  <p>I have HTML code in QString variables. In this code I want to insert data from a database.</p>
  
  <p>I get an error:</p>
  
  <pre><code>E:\apprendreQt\gestionstock6\vente.cpp:117: error: invalid operands of types 
    'const char*' and 'const char [27]' to binary 'operator+'
  </code></pre>
  
  <p>How can I fix this?</p>
  
  <p>Here is my code:</p>
  
  <pre><code>int num_bl = ui-&gt;numeroBLlineEdit-&gt;text().toInt() ;
  QString html;
  QString requette = "select num_facture,date,nom,prenom,code_fiscale,designation,qte_out, prix,(qte_out * prix ) as Montant, sum(qte_out * prix) as Total from ventes join produits_en_ventes join clients  join produits on ventes.vente_id = produits_en_ventes.vente_id and ventes.client_id = clients.client_id and produits_en_ventes.produit_id = produits.produit_id where ventes.client_id = :client_id ";
  
  if(!m_db-&gt;isOpen())
      QMessageBox::critical(this,tr("Inventoria Solution"),m_db-&gt;lastError().text()) ;
  else{
      m_query-&gt;clear();
      m_query-&gt;prepare(requette);
      m_query-&gt;bindValue(":client_id ", num_bl);
  
      if(!m_query-&gt;exec())
          QMessageBox::critical(this,tr("Inventoria Solution"),m_query-&gt;lastError().text()) ;
      else{
          html += "       &lt;table&gt;"
                  "&lt;thead&gt;"
                  "&lt;tr&gt;"
                  "&lt;th&gt;N°&lt;/th&gt;"
                  "&lt;th&gt;Désignation&lt;/th&gt;"
                  "&lt;th&gt;Qte&lt;/th&gt;"
                  "&lt;th&gt;Prix Unitaire&lt;/th&gt;"
                  "&lt;th&gt;Montant&lt;/th&gt;"
                  "   &lt;/tr&gt;"
                  "&lt;/thead&gt;";
          while(m_query-&gt;next())
          {
              int num_article = 1;
  
              html += "&lt;tr&gt; &lt;td&gt;" + num_article + "&lt;/td&gt; &lt;td&gt;"+m_query-&gt;value(5).toString()+"&lt;/td&gt; &lt;td&gt;"+m_query-&gt;value(6).toInt() + "&lt;/td&gt; &lt;td&gt;"+m_query-&gt;value(7).toInt() + "&lt;/td&gt; &lt;td&gt;" + m_query-&gt;value(8).toInt() + "&lt;/td&gt;&lt;/tr&gt;";
              num_article++;
  
          }
              html += "&lt;tfoot&gt;"
                  "&lt;tr&gt;"
                  "&lt;td&gt;Total:"+ m_query-&gt;value(9).toInt()+"&lt;/td&gt;"
                  "&lt;/tr&gt;"
                  "&lt;/tfoot&gt;"
                  "&lt;/table&gt;";
      }
      print_Html(html);
  
  
  }
  </code></pre>