Use QProcess in Qt to back up and restore the Mysql database

UseQtDoMySQL databaseDevelopment, encountered the need to back up and restore the database issues.MySQLThere is no SQL statement used to compile the database into A. SQL file, and a mysqldump.exe tool is used to complete this function. Without SQL statements, QSqlQuery cannot be used.QProcess.

HoweverQtUsed inQProcess: The execute () method cannot export data. Even more depressing is that the Qt Command promptcommand tool provided by Qt cannot find the mysqldump.exe program,
At first, I suspected that the command does not support commands other than the Windows/System32 directory commands?
.
Search for "qt back up Mysql Database" online, and find the cause of the problem. This article "notes when using QProcess: execute () in Qt", uses the QProcess: execute () method in Qt programs in Windows, and cannot use pipelines or redirection operators, to redirect the content to a file or read the input from the file, you must set the standard input and output files of the QProcess object as needed.

Generally, the command line programs used in Windows are rarely useful for pipelines and redirection, because the Windows console itself does not support pipelines and redirection operations.

However, this mysqldump is a special case. It needs to redirect the output to a file.

But like

 
 

  
  
QProcess::execute("mysqldump.exe -uUsrName -pUsrPsd DbName > d:/backup.sql") 
 
 

The function cannot be executed, at least in windows.

QProcess provides setStandardInputFile (), setStandardOutputFile (), and setStandardOutputProcess () starting from Qt4.2 (). three functions are used to handle MPs queue and redirection problems in Windows. Use the start () method instead of the execute () method, and then use setStandardOutputFile () to redirect the output or input.

Specifically, the mysqldump operation should be written as follows:

 
 

  
  
QString Cmd = QString("mysqldump.exe --add-drop-table -u%1 -p%2 test").arg("UsrName","UsrPsd");    
  
  
QString Path = QString("%1").arg("d://backup.Sql");    
  
  
QProcess *poc=new QProcess;    
  
  
poc->setStandardOutputFile(Path);    
  
  
poc->start(Cmd);    
  
  
    QString Cmd = QString("mysqldump.exe --add-drop-table -u%1 -p%2 test").arg("UsrName","UsrPsd");  
  
  
    QString Path = QString("%1").arg("d://backup.Sql");  
  
  
    QProcess *poc=new QProcess;  
  
  
    poc->setStandardOutputFile(Path);  
  
  
    poc->start(Cmd); 
 
 

The corresponding database restoration operations should be written as follows:

 
 

  
  
QString Cmd = QString("mysql.exe -u%1 -p%2 test").arg("UsrName","UsrPsd");    
  
  
QString Path = QString("%1").arg("d://backup.Sql");    
  
  
QProcess *poc=new QProcess;    
  
  
poc->setStandardInputFile(Path);    
  
  
poc->start(Cmd);   
 
 

Summary: InQtUsed inQProcessBackup and recoveryMysql databaseI hope this article will help you!