Qt中SQLite3的增、删、改、查操作

QT & sqlite3:

先说一下QT自带数据库sqlite3和另外用sqlite3插件的区别，他们的功能是一样的，但是代码就不一样了。QT对数据库具有完善的支持，不需要加任何其他插件就可以直接使用，但是如果你要是加了sqlite3插件，调用数据库就跟直接调用一个驱动一样，直接调用接口函数:open、close、……，换言之QT自带的数据库语言就用不上了。

一、使用Qt自带的数据库sqlite3

Qt自带了很多常用的数据库驱动，使用起来非常方便如下图所示：

使用Qt自带数据库SQLite3的代码实例：

Connect to Sqlite and do insert, delete, update and select

  

Foundations of Qt Development\Chapter13\sqltest\sqlite\main.cpp
/*
 * Copyright (c) 2006-2007, Johan Thelin
 * 
 * All rights reserved.
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 * are permitted provided that the following conditions are met:
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 *       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
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 */

#include <QApplication>

#include <QtSql>
#include <QtDebug>

int main( int argc, char **argv )
{
  QApplication app( argc, argv );
   //创建连接
  QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );//第二个参数可以设置连接名字，这里为default

  db.setDatabaseName( "./testdatabase.db" );// 设置数据库名与路径, 此时是放在上一个目录
  //打开连接
  if( !db.open() )
  {
    qDebug() << db.lastError();
    qFatal( "Failed to connect." );
  }
    
  qDebug( "Connected!" );
  //各种操作
  QSqlQuery qry;
  //创建table
  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!";
    //增
  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!" );
//查询
  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() );
  }
  //更新
  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!" );
  //删除
  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;
}