有关性的网站百度seo排名
案例需求：
完成数据库插入，删除，修改，查看操作。
分为 插入，删除，修改，查看，查询 几个模块。
代码：
widget.h
#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QDebug>
#include <QSqlError>
#include <QDateTime>namespace Ui {
class Widget;
}class Widget : public QWidget
{Q_OBJECTpublic:explicit Widget(QWidget *parent = nullptr);~Widget();void display();private slots:void on_insert_button_clicked();void on_delete_button_clicked();void on_update_button_clicked();void on_query_button_clicked();private:Ui::Widget *ui;QSqlDatabase db;QSqlQuery *query;
};#endif // WIDGET_H
widget.cpp
#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget)
{ui->setupUi(this);this->setWindowTitle("数据库可视化窗口");// 加载数据库的驱动db = QSqlDatabase::addDatabase("QSQLITE");// 设置本地数据库文件db.setDatabaseName("stu.db");// 打开数据库if(db.open()) qDebug()<<"打开成功....";else qDebug()<<"打开失败....";// 向数据库发送sql语句query = new QSqlQuery; // 不可指定父对象if(query->exec("CREATE TABLE IF NOT EXISTS stu_info (id INT PRIMARY KEY,name STRING(32),score DOUBLE)"))qDebug()<<"创建table成功....";else qDebug()<<"创建table失败:"<<query->lastError().text();// 显示display();
}Widget::~Widget()
{delete ui;delete query; // 因为调用时不能指定父对象，所以需要手动释放// 关闭数据库db.close();}
// displlay
void Widget::display(){query->exec(QString("SELECT * FROM stu_info"));while(query->next()){int id = query->value("id").toInt();QString name = query->value("name").toString();double score = query->value("score").toDouble();ui->plainTextEdit->appendPlainText(QString("id : %1 | name : %2 | score : %3").arg(id).arg(name).arg(score));}
}
// insert
void Widget::on_insert_button_clicked(){QDateTime currentDate = QDateTime::currentDateTime();QString dateTimeString = currentDate.toString("yyyy-MM-dd hh:mm:ss");if(ui->num_edit->text() == "" || ui->name_edit->text() == "" || ui->score_edit->text() == ""){qDebug()<<"信息缺失 插入失败："<<query->lastError().text();ui->plainTextEdit->appendPlainText(QString("%1 信息缺失 插入失败....").arg(dateTimeString));return ;}int num = ui->num_edit->text().toInt();QString name = ui->name_edit->text();double score = ui->score_edit->text().toDouble();if(query->exec(QString("INSERT INTO stu_info VALUES('%1','%2','%3')").arg(num).arg(name).arg(score))){qDebug()<<dateTimeString<<"插入成功....";ui->plainTextEdit->appendPlainText(QString("%1 插入成功....").arg(dateTimeString));display();}else{qDebug()<<"插入失败："<<query->lastError().text();ui->plainTextEdit->appendPlainText(QString("%1 插入失败....").arg(dateTimeString));}
}
// delete
void Widget::on_delete_button_clicked()
{QDateTime currentDate = QDateTime::currentDateTime();QString dateTimeString = currentDate.toString("yyyy-MM-dd hh:mm:ss");if(ui->num_edit->text() == ""){qDebug()<<dateTimeString<<"学号不存在 删除失败....";ui->plainTextEdit->appendPlainText(QString("%1 学号不存在 删除失败....").arg(dateTimeString));}else if(query->exec(QString("DELETE FROM stu_info WHERE id = %1").arg(ui->num_edit->text().toInt()))){qDebug()<<dateTimeString<<"删除成功....";ui->plainTextEdit->appendPlainText(QString("%1 删除成功....").arg(dateTimeString));display();}else{qDebug()<<"删除失败："<<query->lastError().text();ui->plainTextEdit->appendPlainText(QString("%1 删除失败....").arg(dateTimeString));}
}
// update
void Widget::on_update_button_clicked()
{QDateTime currentDate = QDateTime::currentDateTime();QString dateTimeString = currentDate.toString("yyyy-MM-dd hh:mm:ss");if(query->exec(QString("UPDATE stu_info SET id = %1, name = '%2', score = %3 WHERE id = %4").arg(ui->num_edit->text().toInt()).arg(ui->name_edit->text()).arg(ui->score_edit->text().toDouble()).arg(ui->num_edit->text().toInt()))){qDebug()<<dateTimeString<<"更新成功....";ui->plainTextEdit->appendPlainText(QString("%1 更新成功....").arg(dateTimeString));display();}else{qDebug()<<"更新失败："<<query->lastError().text();ui->plainTextEdit->appendPlainText(QString("%1 更新失败....").arg(dateTimeString));}
}
// query
void Widget::on_query_button_clicked()
{//SELECT * FROM stu_info WHERE id = %1QDateTime currentDate = QDateTime::currentDateTime();QString dateTimeString = currentDate.toString("yyyy-MM-dd hh:mm:ss");if(query->exec(QString("SELECT * FROM stu_info WHERE id = %1").arg(ui->num_edit->text().toInt()))){qDebug()<<dateTimeString<<"查询成功....";ui->plainTextEdit->appendPlainText(QString("%1 查询成功....").arg(dateTimeString));// 显示while(query->next()){int id = query->value("id").toInt();QString name = query->value("name").toString();double score = query->value("score").toDouble();ui->plainTextEdit->appendPlainText(QString("id : %1 | name : %2 | score : %3").arg(id).arg(name).arg(score));}}else{qDebug()<<"查询失败："<<query->lastError().text();ui->plainTextEdit->appendPlainText(QString("%1 查询失败....").arg(dateTimeString));}
}
widget.ui
输出：
初始界面：
插入：
修改：
删除：
查询：
