c++ - 如何在 Qt 中进行 MySQL 查询？

Question

我正在尝试创建一个简单的应用程序，它允许用户输入单词，应用程序将输出定义。我通过制作mysql数据库文件来编译单词和定义。我认为使用 MySQL 是制作我的应用程序的更快方法。我的数据库如下所示:

rowed      |  Column1(word)           | Column2(definition)
1               DNA                      A double-stranded,helical...

这个程序的伪代码肯定应该是这样的:

if(lineEdit == wordInput)
{ 
    ui->label->setText("Display definition)
} 

我只是不知道该怎么做。到目前为止，我已经尝试过以下代码:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
#include <QDebug>
#include <QPalette>

#define Path_to_DB "/Users/makkhay/Desktop/nep_eng-2.sqlite"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)

{
    ui->setupUi(this);
       // Set background picture
       QPixmap bkgnd("/Users/makkhay/Desktop/background.jpg");
       bkgnd = bkgnd.scaled(this->size(), Qt::IgnoreAspectRatio);
       QPalette palette;
       palette.setBrush(QPalette::Background, bkgnd);
       this->setPalette(palette);


       myDB = QSqlDatabase::addDatabase("QSQLITE");
       myDB.setDatabaseName(Path_to_DB);
       QFileInfo checkFile(Path_to_DB);

       if(checkFile.isFile())
       {
           if(myDB.open())
           {
             ui->label->setText("The database is connected");
           }

       }else{
           ui->label->setText("No file found!");
       }


}

MainWindow::~MainWindow()
{
    delete ui;
    myDB.close();
}


void MainWindow::on_pushButton_clicked()
{
//    QMessageBox::StandardButton reply= QMessageBox::question(this,
//                                      "My Title", " Word not found, quit app?",
//                                       QMessageBox::Yes | QMessageBox::No);


//    if(reply == QMessageBox::Yes){

//        QApplication::quit();
//}


    if(!myDB.isOpen()){
        qDebug() << " No connection to db";
        return;
    }

    QString wordInput, definition;
    wordInput = ui->lineEdit->text();

    QSqlQuery qry;

    qry.prepare("SELECT Column1,Column2 FROM Nepali WHERE Column1  = :input");
    qry.bindValue(":input",wordInput);
   // int fieldNo = query.record().indexof("Column1");

    if(qry.exec())
    {
        ui->debug->setText(" Checking output!");  // output is visible 

      while (qry.next())
       {
         ui->output->setText("Checing output!");  // output is not visible


        QString inputWord = qry.value(0).toString();
        QString wordDefinition = qry.value(1).toString();
        ui->output->setText(wordDefinition);





      }
    }

}

Answer 1

好的，下面的代码对我有用。尝试注释掉您现有的代码并粘贴此代码。此代码基本上与您发布的代码完全相同，我只是注释掉了一些设置背景的代码并删除了一些多余的行。

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
#include <QDebug>
#include <QPalette>
#include <QSqlQuery>
#include <QFileInfo>

#define Path_to_DB "/Users/makkhay/Desktop/nep_eng-2.sqlite"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)

{
    ui->setupUi(this);
       // Set background picture
       //QPixmap bkgnd("/Users/makkhay/Desktop/background.jpg");
       //bkgnd = bkgnd.scaled(this->size(), Qt::IgnoreAspectRatio);
       //QPalette palette;
       //palette.setBrush(QPalette::Background, bkgnd);
       //this->setPalette(palette);


       myDB = QSqlDatabase::addDatabase("QSQLITE");
       myDB.setDatabaseName(Path_to_DB);
       QFileInfo checkFile(Path_to_DB);

       if(checkFile.isFile())
       {
           if(myDB.open())
           {
             ui->label->setText("The database is connected");
           }

       }else{
           ui->label->setText("No file found!");
       }


}

MainWindow::~MainWindow()
{
    delete ui;
    myDB.close();
}


void MainWindow::on_pushButton_clicked()
{
    if(!myDB.isOpen()){
        qDebug() << " No connection to db";
        return;
    }

    QString wordInput;
    wordInput = ui->lineEdit->text();

    QSqlQuery qry;

    qry.prepare("SELECT Column1,Column2 FROM Nepali WHERE Column1  = :input");
    qry.bindValue(":input",wordInput);

    if(qry.exec())
    {
        ui->debug->setText(" Checking output!");

      while (qry.next())
      {
         // Retrieve Values from select statement
         QString inputWord = qry.value(0).toString();
         QString wordDefinition = qry.value(1).toString();

         // Display values
         ui->output->setText(wordDefinition);
      }
    } else {
        qDebug() << "query failed to execute";
    }

}