Qt开发之路——SQlite的使用（简单粗暴）

SQlite是一个轻便的数据库，在Qt中有内置驱动，无需安装即可使用，非常方便。本文内容包括数据库的建创建，连接，打开，数据表的创建，数据表内容的增删查操作。涉及的代码均为自己做的项目中的,没有考虑代码屯余问题，注释清晰，方便学习理解，有任何问题可以留言，共同进步~

ok，上才艺~

首先
QT += sql

数据库的创建，连接和打开
qt_sql_default_connection是数据库默认名

void Widget::createDatabase(){
    //create and connect the database
    QSqlDatabase database;
    if (QSqlDatabase::contains("qt_sql_default_connection"))
    {
        database = QSqlDatabase::database("qt_sql_default_connection");
    }
    else
    {
        database = QSqlDatabase::addDatabase("QSQLITE");
        database.setDatabaseName("MyDataBase.db");
    }
    //open the database
    if (!database.open())
    {
        qDebug() << "Error: Failed to connect database." << database.lastError();
    }
    else
    {
        qDebug() <<"数据库连接成功！"<<"从数据库读取数据.";
    }
}

数据库准备，数据表创建，插入数据
操作表之前要做好数据库的准备，这里的数据插入是我项目中涉及到的一个treewidget中的数据，当然可以直接插入数据，仅供参考

void Widget::writeDatabase()
{
    //create and connect database
    QSqlDatabase database;
    if (QSqlDatabase::contains("qt_sql_default_connection"))
    {
        database = QSqlDatabase::database("qt_sql_default_connection");
    }
    else
    {
        database = QSqlDatabase::addDatabase("QSQLITE");
        database.setDatabaseName("MyDataBase.db");
    }

    //create table
    QSqlQuery sql_query;//set id text primary key

    //judge table exist or not
    bool isTableExist = \
        sql_query.exec(QString("select count(*) from realdata where type='table' and name='%1'").arg(("realdata")));
    if(!isTableExist){
        if(!sql_query.exec("create table realdata(id text,manufacturer text,powerstate text,serveritynum text,uuid text,health text)"))
        {
            qDebug() << "Error: Fail to create table."<< sql_query.lastError();
        }
        else
        {
            qDebug() << "Table created!";
        }
    }
    else{
    }

    //ergodic the treewidget item,insert the data into database
    QTreeWidgetItemIterator it(ui->treeWidget->currentItem());
    while(*it){
        (*it)->setHidden(false);
        QTreeWidgetItem *item = *it;
        if(!sql_query.exec(QString("INSERT INTO realdata VALUES('%1','%2','%3','%4','%5','%6')").arg(item->text(0)).arg(item->text(1)).arg(item->text(2)).arg(item->text(3)).arg(item->text(4)).arg(item->text(5))))
        {
            qDebug() << "insert !!" <<sql_query.lastError();
        }
        else
        {
            qDebug() << "inserted FirstItemData!";
        }
        ++it;
    }

    //close database
    database.close();
}

删除整个数据表
操作表之前要做好数据库的准备，本函数可用于清楚所有数据，类似于一键删除的功能

void Widget::deleteRealData(){

    //create and connect database
    QSqlDatabase database;
    if (QSqlDatabase::contains("qt_sql_default_connection"))
    {
        database = QSqlDatabase::database("qt_sql_default_connection");
    }
    else
    {
        database = QSqlDatabase::addDatabase("QSQLITE");
        database.setDatabaseName("MyDataBase.db");
    }

    //delete the table
    QSqlQuery sql_query;
    sql_query.exec("drop table realdata");
    if(sql_query.exec())
    {
        qDebug() << sql_query.lastError();
    }
    else
    {
        qDebug() << "table cleared";
    }
}

查看数据
查看数据之后是对treewidget的使用，仅供参考

void Widget::readRealData(){

    createDatabase();

    //read data
    QSqlQuery sql_query;

    sql_query.exec("select * from realdata");
    if(!sql_query.exec())
    {
        qDebug()<<sql_query.lastError();
    }
    else
    {
        qDebug()<<"表：";
        //read database
        while(sql_query.next())
        {
            QString id = sql_query.value(0).toString();
            QString manufacturer= sql_query.value(1).toString();
            QString powerstate = sql_query.value(2).toString();
            QString serveritynum = sql_query.value(3).toString();
            QString uuid = sql_query.value(4).toString();
            QString health = sql_query.value(5).toString();
            qDebug()<<QString("id:%1    manufacturer:%2    powerstate:%3   serveritynum:%4   uuid:%5  health:%6").arg(id).arg(manufacturer).arg(powerstate).arg(serveritynum).arg(uuid).arg(health);
            QStringList strs;

            //
            strs<<QString(id)<<QString(manufacturer)<<QString(powerstate)<<QString(serveritynum)<<QString(uuid);

            //add one line for treewidget,content is strs
            QTreeWidgetItem *strsroot = new QTreeWidgetItem(ui->treeWidget,strs);

            //set the header to appropriate size
            QHeaderView *head=ui->treeWidget->header();
            head->setSectionResizeMode(QHeaderView::ResizeToContents);

            ui->treeWidget->setCurrentItem(strsroot);//set currentitem
      
        }
        qDebug()<<"成功显示在界面上.";
    }
}

走过的冤枉路——SQL语句

一定要注意一点！！！sql语句中用到arg时，%1要带‘’，也就是’%1’,’%2’,否则会报错，QSqlError(“1“, “Unable to execute statement“, “near \“.73\“: syntax error“)

参考
这两篇参考写的比较好，可以看一看
https://blog.csdn.net/weixin_41656968/article/details/80473137
https://www.cnblogs.com/xia-weiwen/archive/2017/05/04/6806709.html

标签：SQlite,Qt,database,text,粗暴,sql,qDebug,query,QSqlDatabase
来源： https://blog.csdn.net/qq_16488989/article/details/112007338