# ConnectAndRead

VTKExamples/Cxx/Databases/SQL/MySQL/ConnectAndRead

### Code

ConnectAndRead.cxx

    #include <vtkSmartPointer.h>
    #include <vtkMySQLDatabase.h>
    #include <vtkSQLQuery.h>
    #include <vtkVariant.h>

    /*
    If you get the error:
    Unsupported protocol: mysql
    It means you must recompile VTK with VTK_USE_MYSQL = ON

    If you get the error:
    vtkMySQLDatabase::New() is not defined
    It means that cmake did not find your mysql include and library
    path correctly (ie.  MYSQL_INCLUDE_DIRECTORIES, etc)
    */

    int main(int, char *[])
    {
      // url syntax:
      // mysql://'[[username[':'password]'@']hostname[':'port]]'/'[dbname]

      vtkSmartPointer<vtkMySQLDatabase> db =
        vtkSmartPointer<vtkMySQLDatabase>::Take(vtkMySQLDatabase::SafeDownCast(
                vtkSQLDatabase::CreateFromURL( "mysql://root@localhost/TestDatabase" ) ));

      bool status = db->Open();

      std::cout << "Database open? " << status << std::endl;

      if(!status)
      {
        return EXIT_FAILURE;
      }

      vtkSmartPointer<vtkSQLQuery> query =
        vtkSmartPointer<vtkSQLQuery>::Take(db->GetQueryInstance());

      std::string createQuery( "SELECT PointId FROM TestTable");
      std::cout << createQuery << std::endl;
      query->SetQuery( createQuery.c_str() );
      query->Execute();

      for ( int col = 0; col < query->GetNumberOfFields(); ++ col )
      {
        if ( col > 0 )
        {
          cerr << ", ";
        }
        cerr << query->GetFieldName( col );
      }
      cerr << endl;
      while ( query->NextRow() )
      {
        for ( int field = 0; field < query->GetNumberOfFields(); ++ field )
        {
          if ( field > 0 )
          {
            cerr << ", ";
          }
          cerr << query->DataValue( field ).ToString().c_str();
        }
        cerr << endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ConnectAndRead)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkIOMySQL
      vtkIOSQL QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ConnectAndRead: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(ConnectAndRead MACOSX_BUNDLE ConnectAndRead.cxx )
      target_link_libraries(ConnectAndRead PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ConnectAndRead MACOSX_BUNDLE ConnectAndRead.cxx )
      target_link_libraries(ConnectAndRead PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ConnectAndRead
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ConnectAndRead

Click here to download ConnectAndRead and its CMakeLists.txt file. Once the tarball ConnectAndRead.tar has been downloaded and extracted,

    cd ConnectAndRead/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./ConnectAndRead

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.