Qt使用SQLITE数据库

1、初始化

void Widget::InitialSQLiteDb()
{
    
    QSqlDatabase m_dbSystemData ;
// 检测已连接的方式 - 默认连接名
// QSqlDatabase::contains(QSqlDatabase::defaultConnection)
// if(QSqlDatabase::contains("qt_sql_default_connection"))
// {
    

// db = QSqlDatabase::database("qt_sql_default_connection");
// }
// else
// {
    
// db = QSqlDatabase::addDatabase("QSQLITE");
// }

    //检测已连接的方式 - 自定义连接名
    if(QSqlDatabase::contains("mysql_connection"))
    {
    

        m_dbSystemData = QSqlDatabase::database("mysql_connection");
    }
    else
    {
    
        m_dbSystemData = QSqlDatabase::addDatabase("QSQLITE","mysql_connection");
    }

    //设置数据库路径，不存在则创建
    m_dbSystemData.setDatabaseName("mySysData.db");
    //db.setUserName();

    //打开数据库
    if(!m_dbSystemData.open())
    {
    
        qDebug()<<"create sqldb failed!";
        return;
    }

    //关闭数据库
    m_dbSystemData.close();
}

2、创建表格

void Widget::CreateTable()
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return;
    }

    //如果不存在则创建my_table表 id自增,name唯一
    const QString sql=R"( CREATE TABLE IF NOT EXISTS my_table ( id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, code INTEGER, name CHAR (50) UNIQUE NOT NULL, age INTEGER, sex INTEGER, score INTEGER, rank INTEGER, address CHAR (50) );)";

    //QSqlQuery构造前，需要db已打开并连接;未指定db或者db无效时使用默认连接进行操作
    QSqlQuery query(m_dbSystemData);

    if(query.exec(sql))
    {
    
        qDebug()<<"create table success!";
    }
    else
    {
    
        //打印sql语句错误信息
        qDebug()<<"create table error!"<< query.lastError();
    }
}

3、插入数据

void Widget::insertRecord(const QString &name, const QString address, int code, int age, int sex, int score, int rank)
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return;
    }

    qDebug()<<"2222!";

    QSqlQuery query(m_dbSystemData);

    //方式一，直接执行SQL语句
    query.exec(QString(R"(INSERT INTO my_table(code,name,age,sex,score,rank,address) VALUES(%1,'%2',%3,%4,%5,%6,'%7');)")
               .arg(code).arg(name).arg(age).arg(sex).arg(score).arg(rank).arg(address));

    //方式二，绑定值，待定变量默认用问号占位,注意字符串也没有引号
    /*query.prepare(R"(INSERT INTO my_table(name,age) VALUES(?,?);)"); query.addBindValue(name); query.addBindValue(age); query.exec();*/
}

4、删除数据

void Widget::deleteRecord(const QString &name)
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return;
    }

    QSqlQuery query(m_dbSystemData);
    //方式一，直接执行SQL语句
    query.exec(QString(R"(DELETE FROM my_table WHERE name='%1';)").arg(name));

    //方式二，绑定值，待定变量默认用问号占位
    /*query.prepare(R"(DELETE FROM my_table WHERE name=?;)"); query.addBindValue(name); query.exec();*/
}

5、更新数据

void Widget::updateRecord(const QString &name, int age)
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return;
    }

    QSqlQuery query(m_dbSystemData);
    //方式一，直接执行SQL语句
    query.exec(QString(R"(UPDATE my_table SET age=%2 WHERE name='%1';)")
               .arg(name).arg(age));
    //方式二，绑定值，待定变量默认问号，可自定义
    /*query.prepare(R"(UPDATE my_table SET age=:age WHERE name=:name;)"); query.bindValue(":name",name);//通过自定义的别名来替代 query.bindValue(":age",age); query.exec();*/
}

6、查询数据

int Widget::searchRecord(const QString &name)
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return -1;
    }

    QSqlQuery query(m_dbSystemData);
    query.exec(QString(R"(SELECT age FROM my_table WHERE name='%1';)").arg(name));

    //获取查询结果的第0个值，
    //如果结果是多行数据，可用while(query.next()){}遍历每一行
    int ageValue=-1;
    if(query.next())
    {
    
        ageValue = query.value(0).toInt();
    }
    qDebug()<<"age value is: "<< ageValue;
    return ageValue;
}

7、初始化表格数据

void Widget::InitialQTable()
{
    
    if(!m_dbSystemData.isOpen())
    {
    
        qDebug()<<"db is not open!";
        return;
    }

    ui->tableWidget->setColumnCount(7);
    //ui->tableWidget->setRowCount(10);
    ui->tableWidget->verticalHeader()->setVisible(false);  //隐藏列表头
    ui->tableWidget->horizontalHeader()->setStretchLastSection(true);
    ui->tableWidget->setSelectionBehavior(QAbstractItemView::SelectRows); //整行选中的方式
    QStringList header;
    header<<"学号"<<"姓名"<<"年龄"<<"性别"<<"总分"<<"排名"<<"地址";
    ui->tableWidget->setHorizontalHeaderLabels(header);

    QSqlQuery query(m_dbSystemData);
    query.exec("SELECT * FROM my_table");

    //如果结果是多行数据，可用while(query.next()){}遍历每一行
    int nRow = 0;
    while(query.next())
    {
    
        int iRow = ui->tableWidget->rowCount();
        ui->tableWidget->setRowCount(iRow + 1);
        int id = query.value(0).toInt();
        QString code = query.value(1).toString();
        QString name = query.value(2).toString();
        QString age = query.value(3).toString();
        int nSex = query.value(4).toInt();
        QString sex;
        if(nSex == 0)
        {
    
            sex = "男";
        }
        else
        {
    
            sex = "女";
        }
        QString score = query.value(5).toString();
        QString rank = query.value(6).toString();
        QString address = query.value(7).toString();

        qDebug()<< id << code << name << age << sex << score << rank;

        ui->tableWidget->setItem(nRow,0,new QTableWidgetItem(code));
        ui->tableWidget->setItem(nRow,1,new QTableWidgetItem(name));
        ui->tableWidget->setItem(nRow,2,new QTableWidgetItem(age));
        ui->tableWidget->setItem(nRow,3,new QTableWidgetItem(sex));
        ui->tableWidget->setItem(nRow,4,new QTableWidgetItem(score));
        ui->tableWidget->setItem(nRow,5,new QTableWidgetItem(rank));
        ui->tableWidget->setItem(nRow,6,new QTableWidgetItem(address));

        nRow++;
    }

    ui->tableWidget->show();
}