Qt数据库连接

 本文实了数据库的增删除改查询功能

#ifndef WIDGET_H
#define WIDGET_H

#include <QtSql/QSql>
#include <QWidget>
#include<QSqlDatabase>
#include <QtSql/qsqlquery.h>
QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE
struct student
{
    QString Name;
    int Age;
    QString Class;
    student(QString name,int age ,QString classs) {
        this->Name=name;
        this->Age=age;
        this->Class = classs;
    }
};
class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
private slots:
    void on_pushButton_clicked();

    void on_pushButton_2_clicked();

private:
    bool try_connect_database();
    void update_value(QSqlDatabase &db,  student&data);
    void insert_date(QSqlDatabase &db,  student&data);
    void delete_data(QSqlDatabase &db,  student&data);
    void search_date(QSqlDatabase &db,  student&data);
private:
    Ui::Widget *ui;
    QSqlDatabase db;
};
#endif // WIDGET_H

#include "widget.h"
#include "ui_widget.h"
#include <QMessageBox>
#include <QSqlRecord>
Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    db = QSqlDatabase::addDatabase("QMYSQL");
    try_connect_database();
    student data{"zhao",11,"8班级"};

}

Widget::~Widget()
{
    if(db.isOpen()){
        db.close();
    }
    delete ui;
}

bool  Widget::try_connect_database(){
    db.setHostName("127.0.0.1");
    db.setPort(3306);
    db.setDatabaseName("students");
    db.setUserName("root");
    db.setPassword("258551");
    bool ok = db.open();
    // chinese show
    db.setConnectOptions("MYSQL_OPT_RECONNECT=1;MYSQL_SET_CHARSET_NAME=utf8mb4");
    if(ok){
        return true;
    }else{
        QMessageBox::information(this, "infor", "link failed");
        return false;
    }

}

void Widget::update_value(QSqlDatabase &db,  student&data){
    if(db.isOpen()){
        return;
    }
    QSqlQuery query;
    query.prepare("update student SET age = :age WHERE name = :name;");
    query.bindValue(":age",data.Age+100,QSql::In);
    query.bindValue(":name",data.Name);
    query.exec();
    qDebug()<<"find execute";

}
void Widget::insert_date(QSqlDatabase &db,  student&data){
    if(!db.isOpen()){
        return;
    }
    QSqlQuery query;

    query.prepare("insert into student (name,age,class) valuse(:Name,:Age,:Class);");
    query.bindValue(":Name",data.Name);
    query.bindValue(":Age",data.Age);
    query.bindValue(":Class",data.Class);
    if(query.exec()){
        qDebug()<<"insert execute";
    }else{
        qDebug()<<"failed execute";
    }

}
void Widget::delete_data(QSqlDatabase &db,  student&data){
    if(!db.isOpen()){
        return;
    }
    QSqlQuery query;

    query.prepare("DELETE FROM student WHERE name = :name;");
    query.bindValue(":name",data.Name);
    if(query.exec()){
        qDebug()<<"insert execute";
    }else{
        qDebug()<<"failed execute";
    }

};
void Widget::search_date(QSqlDatabase &db,  student&data){
    if(!db.isOpen()){
        return;
    }
    data.Name = "zhao1";
    QSqlQuery query;

    query.prepare("DELETE * FROM student WHERE name = :name;");
    query.bindValue(":name",data.Name);
    query.exec();
    QSqlRecord recodes= query.record();
    //
    while(query.next()){

        for(int i = 0 ;i <recodes.count();i++){

            QVariant value = query.value(i);
            qDebug() << "Column" << i << ":" << value.toString();
        }
    }

}

void Widget::on_pushButton_clicked()
{
    if(!db.isOpen()){
        return;
    }
    QSqlQuery query;
    student data{"zhao",11,"8班级"};
    query.prepare("update student SET age = :age WHERE name = :name;");
    query.bindValue(":age",data.Age+1000,QSql::In);
    query.bindValue(":name",data.Name);
    if(query.exec()){
        qDebug()<<"find execute";
    }else{
        qDebug()<<"failed execute";
    }

}


void Widget::on_pushButton_2_clicked()
{
    if(!db.isOpen()){
        return;
    }
    student data{"zhao1",11,"8班级"};
    QSqlQuery query;

    query.prepare("SELECT * FROM student WHERE name = :name;");
    query.bindValue(":name",data.Name);
    query.exec();
    QSqlRecord recodes= query.record();
    //
    while(query.next()){

        for(int i = 0 ;i <recodes.count();i++){

            QVariant value = query.value(i);
            qDebug() << "Column" << i << ":" << value.toString();
        }
    }

}