i am building a small project having following slot :-
Qt Code: 
  1. void DialogMemberAdd::query(QString *qry, int flag)
  2. {
  3.     QString sql = *qry;
  4.     QString str;
  5.     QSqlQuery qry2;
  6.     qry2.prepare(sql);
  7.  
  8.     if(ui->lineEditName->text().isEmpty())
  9.     {
  10.         //str = "NULL";
  11.         return;
  12.     }
  13.     else
  14.     {
  15.         str = ui->lineEditName->text().trimmed();
  16.     }
  17.     qry2.bindValue(0, str) ;
  18.  
  19.     int cardno = 0;
  20.     if(ui->lineEditCardNumber->text().trimmed().isEmpty())
  21.     {
  22.         cardno = 0;
  23.     }
  24.     else
  25.     {
  26.         cardno = ui->lineEditCardNumber->text().trimmed().toInt();
  27.     }
  28.     qry2.bindValue(1, cardno);
  29.  
  30.     QString addr;
  31.     if(ui->lineEditAddress->text().trimmed().isEmpty())
  32.     {
  33.         addr = "";
  34.     }
  35.     else
  36.     {
  37.         addr = ui->lineEditAddress->text().trimmed();
  38.     }
  39.     qry2.bindValue(2, addr);
  40.  
  41.     long  monum = 0;
  42.     if(ui->lineEditMobileNumber->text().trimmed().isEmpty())
  43.     {
  44.         monum = 0;
  45.     }
  46.     else
  47.     {
  48.         monum = ui->lineEditMobileNumber->text().trimmed().toLong();
  49.     }
  50.     qry2.bindValue(3, monum);
  51.  
  52.     float amount;
  53.     if(ui->lineEditAmopuntDeposited->text().trimmed().isEmpty())
  54.     {
  55.         amount = 0.0;
  56.     }
  57.     else
  58.     {
  59.         amount = ui->lineEditAmopuntDeposited->text().trimmed().toFloat();
  60.     }
  61.     qry2.bindValue(4, amount);
  62.     long long memno;
  63.     if(ui->lineEditMembershipNumber->text().trimmed().isEmpty())
  64.     {
  65.         memno = 0;
  66.     }
  67.     else
  68.     {
  69.         memno = ui->lineEditMembershipNumber->text().trimmed().toInt();
  70.     }
  71.  
  72.     qry2.bindValue(5, memno);
  73.  
  74.     if(qry2.exec())
  75.     {
  76.         if(flag == 1)
  77.         {
  78.             QMessageBox::information(this, "insert_into member records ", "Records inserted successfully");
  79.         }
  80.         else if(flag == 2)
  81.         {
  82.             QMessageBox::information(this, "insert_into member records ", "Records updated successfully");
  83.         }
  84.     }
  85.     else
  86.     {
  87.         QMessageBox::critical(this,"insert_into member records ", QString("error = ").append(qry2.lastError().text()) );
  88.     }
  89. }
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and signal is :-
Qt Code: 
  1. void query_sql(QString *sql, int flags);
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here i send this signal as follows :-
Qt Code: 
  1. void DialogMemberAdd::on_pushButtonModifyRecord_clicked()
  2. {
  3.     QString sql = "update tableMemberRecords set name = ?, cardno = ?, address = ?, mobileno = ?, amountdeposited = ?, membershipno = ?";
  4.     flag = 2;
  5.     emit query_sql(&sql, flag);
  6. }
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when running and clicking on pushbutton it shows following error :-
Qt Code: 
  1. "Duplicate entry '9630612822' for key 'MobileNo_UNIQUE' QMYSQL3: Unable to execute statement."
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even it is already having that entry in database.How to get rid of this duplicate entry.