Connect to MySql with QSqlDatabase, and do select, update, insert and delete : QSqlDatabase « Qt « C++






Connect to MySql with QSqlDatabase, and do select, update, insert and delete

  


Foundations of Qt Development\Chapter13\sqltest\mysql\main.cpp
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice, 
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright notice,  
 *       this list of conditions and the following disclaimer in the documentation 
 *       and/or other materials provided with the distribution.
 *     * Neither the name of APress nor the names of its contributors 
 *       may be used to endorse or promote products derived from this software 
 *       without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <QApplication>

#include <QtSql>
#include <QtDebug>

int main( int argc, char **argv )
{
  QApplication app( argc, argv );

  QSqlDatabase db = QSqlDatabase::addDatabase( "QMYSQL" );

  db.setHostName( "localhost" );
  db.setDatabaseName( "qtbook" );

  db.setUserName( "root" );
  db.setPassword( "sa" );

  if( !db.open() )
  {
    qDebug() << db.lastError();
    qFatal( "Failed to connect." );
  }
    
  qDebug( "Connected!" );
  
  QSqlQuery qry;

  qry.prepare( "CREATE TABLE IF NOT EXISTS names (id INTEGER UNIQUE PRIMARY KEY, firstname VARCHAR(30), lastname VARCHAR(30))" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug() << "Table created!";
    
  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (1, 'John', 'Doe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (2, 'Jane', 'Doe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (3, 'James', 'Doe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (4, 'Judy', 'Doe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (5, 'Richard', 'Roe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (6, 'Jane', 'Roe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (7, 'John', 'Noakes')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (8, 'Donna', 'Doe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO names (id, firstname, lastname) VALUES (9, 'Ralph', 'Roe')" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

// SALARIES
  qry.prepare( "CREATE TABLE IF NOT EXISTS salaries (id INTEGER UNIQUE PRIMARY KEY, annual INTEGER)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (1, 1000)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (2, 900)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (3, 900)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (5, 1100)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (6, 1000)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (8, 1200)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "INSERT INTO salaries (id, annual) VALUES (9, 1200)" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Inserted!" );

  qry.prepare( "SELECT * FROM salaries" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    int cols = rec.count();
    
    QString temp;
    for( int c=0; c<cols; c++ )
      temp += rec.fieldName(c) + ((c<cols-1)?"\t":"");
    qDebug() << temp;
      
    while( qry.next() )
    {
      temp = "";
      for( int c=0; c<cols; c++ )
        temp += qry.value(c).toString() + ((c<cols-1)?"\t":"");
      qDebug() << temp;
    }
  }

  qry.prepare( "SELECT names.firstname, names.lastname, salaries.annual FROM names JOIN salaries ON names.id = salaries.id" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    int cols = rec.count();
    
    QString temp;
    for( int c=0; c<cols; c++ )
      temp += rec.fieldName(c) + ((c<cols-1)?"\t":"");
    qDebug() << temp;
      
    while( qry.next() )
    {
      temp = "";
      for( int c=0; c<cols; c++ )
        temp += qry.value(c).toString() + ((c<cols-1)?"\t":"");
      qDebug() << temp;
    }
  }

  qry.prepare( "SELECT names.firstname, names.lastname, salaries.annual FROM names LEFT JOIN salaries ON names.id = salaries.id" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    int cols = rec.count();
    
    QString temp;
    for( int c=0; c<cols; c++ )
      temp += rec.fieldName(c) + ((c<cols-1)?"\t":"");
    qDebug() << temp;
      
    while( qry.next() )
    {
      temp = "";
      for( int c=0; c<cols; c++ )
        temp += qry.value(c).toString() + ((c<cols-1)?"\t":"");
      qDebug() << temp;
    }
  }

  qry.prepare( "SELECT names.lastname, SUM(salaries.annual)/COUNT(*) AS 'Average', MIN(salaries.annual) AS 'Minimum', MAX(salaries.annual) AS 'Maximum' FROM names LEFT JOIN salaries ON names.id = salaries.id GROUP BY names.lastname" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    int cols = rec.count();
    
    QString temp;
    for( int c=0; c<cols; c++ )
      temp += rec.fieldName(c) + ((c<cols-1)?"\t":"");
    qDebug() << temp;
      
    while( qry.next() )
    {
      temp = "";
      for( int c=0; c<cols; c++ )
        temp += qry.value(c).toString() + ((c<cols-1)?"\t":"");
      qDebug() << temp;
    }
  }
// SALARIES

  qry.prepare( "SELECT * FROM names" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    
    int cols = rec.count();
    
    for( int c=0; c<cols; c++ )
      qDebug() << QString( "Column %1: %2" ).arg( c ).arg( rec.fieldName(c) );
      
    for( int r=0; qry.next(); r++ )
      for( int c=0; c<cols; c++ )
        qDebug() << QString( "Row %1, %2: %3" ).arg( r ).arg( rec.fieldName(c) ).arg( qry.value(c).toString() );
  }
  
  
  qry.prepare( "SELECT firstname, lastname FROM names WHERE lastname = 'Roe'" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    
    int cols = rec.count();
    
    for( int c=0; c<cols; c++ )
      qDebug() << QString( "Column %1: %2" ).arg( c ).arg( rec.fieldName(c) );
      
    for( int r=0; qry.next(); r++ )
      for( int c=0; c<cols; c++ )
        qDebug() << QString( "Row %1, %2: %3" ).arg( r ).arg( rec.fieldName(c) ).arg( qry.value(c).toString() );
  }


  qry.prepare( "SELECT firstname, lastname FROM names WHERE lastname = 'Roe' ORDER BY firstname" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    
    int cols = rec.count();
    
    for( int c=0; c<cols; c++ )
      qDebug() << QString( "Column %1: %2" ).arg( c ).arg( rec.fieldName(c) );
      
    for( int r=0; qry.next(); r++ )
      for( int c=0; c<cols; c++ )
        qDebug() << QString( "Row %1, %2: %3" ).arg( r ).arg( rec.fieldName(c) ).arg( qry.value(c).toString() );
  }


  qry.prepare( "SELECT lastname, COUNT(*) as 'members' FROM names GROUP BY lastname ORDER BY lastname" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
  {
    qDebug( "Selected!" );
    
    QSqlRecord rec = qry.record();
    
    int cols = rec.count();
    
    for( int c=0; c<cols; c++ )
      qDebug() << QString( "Column %1: %2" ).arg( c ).arg( rec.fieldName(c) );
      
    for( int r=0; qry.next(); r++ )
      for( int c=0; c<cols; c++ )
        qDebug() << QString( "Row %1, %2: %3" ).arg( r ).arg( rec.fieldName(c) ).arg( qry.value(c).toString() );
  }
  
  qry.prepare( "UPDATE names SET firstname = 'Nisse', lastname = 'Svensson' WHERE id = 7" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Updated!" );

  qry.prepare( "UPDATE names SET lastname = 'Johnson' WHERE firstname = 'Jane'" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Updated!" );
  
  qry.prepare( "DELETE FROM names WHERE id = 7" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Deleted!" );

  qry.prepare( "DELETE FROM names WHERE lastname = 'Johnson'" );
  if( !qry.exec() )
    qDebug() << qry.lastError();
  else
    qDebug( "Deleted!" );
    
  db.close();

  return 0;
}

   
    
  








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