QT: database connection, opening, and getting the number of fields and rows of the table in the DB

database initialization

 //1选择数据库类型并连接
  QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
  QString dbName="mydb.db";
  db.setDatabaseName(dbName);
  //2打开数据库
    if (!db.open())
    {
    
    
        qDebug()<<"Database Error"<<db.lastError().text();
        return ;
    }
   //3启动数据库相关操作指令
    QSqlQuery query;
    query = QSqlQuery(db);

Get the number of fields in a table

    QSqlTableModel *tableModel;
    tableModel = new QSqlTableModel(this, db);
    QString TableName="table1";
    tableModel->setTable(TableName);
    tableModel->select();
    int nRecordCount = tableModel->rowCount();
    int nColumnCount=tableModel->columnCount();
    QString TempStr=TableName+QString("行数=%1").arg(nRecordCount);
    TempStr=TableName+QString("列数=%1").arg(nColumnCount);