C / C++ / MFC

for (int row=0;dbdataset->Rows->Count;row++)	

for (int row=0;row < dbdataset->Rows->Count;row++)	

for (int row=0;0 < dbdataset->Rows->Count;row++)

for (int row=0;dbdataset->Rows->Count;row++)

for (int row=0; row < dbdataset->Rows->Count; row++)

MySqlCommand^CmdDataBase = gcnew MySqlCommand("select * from world.city",conDataBase);
                try{
                    conDataBase->Open();
                    MySqlDataAdapter^sda= gcnew MySqlDataAdapter();
                    sda->SelectCommand=CmdDataBase;
                    DataTable^dbdataset=gcnew DataTable();
                    DataColumn^rt_col=gcnew DataColumn();
                    rt_col->ColumnName = "Ret";
                    rt_col->DataType=System::Type::GetType("System.Double");
                    dbdataset->Columns->Add(rt_col);

DataRow^rt_row;


                     for (int row=0;row<dbdataset->Rows->Count;row++)
                     {
                         rt_row=dbdataset->NewRow();
                         rt_row["Ret"]=log(System::Convert::ToDouble(rt_row["Population"][row])/System::Convert::ToDouble(rt_row["Population"][row-1]));
                         //rt_row["DataReturn"]=System::Convert::ToDouble(dbdataset->Rows[row]["Population"])/System::Convert::ToDouble(dbdataset->Rows[row-1]["Population"]);
                         dbdataset->Rows->Add(rt_row);

Member 11230372 wrote:

2-adding an extra column "ret" to dbdataset

Member 11230372 wrote:

3-fill "ret" rows based on values from column "Population"

for (int row=0; row < dbdataset->Rows->Count; row++)
{
    rt_row=dbdataset->Rows[row];
    rt_row["Ret"] = log(System::Convert::ToDouble(rt_row["Population"]) /  --> not sure what this calculation should be
// System::Convert::ToDouble(rt_row["Population"][row-1]));
    //rt_row["DataReturn"]=System::Convert::ToDouble(dbdataset->Rows[row]["Population"])/System::Convert::ToDouble(dbdataset->Rows[row-1]["Population"]);
//    dbdataset->Rows->Add(rt_row);
}

DataColumn^rt_col=gcnew DataColumn();
                     rt_col->ColumnName = "Ret";
                     rt_col->DataType=System::Type::GetType("System.Double");
                     dbdataset->Columns->Add(rt_col);

"No, it still makes no sense. You add an extra column to your table and then you say you need to store information in extra rows. Choose one or the other."
 
I've added an extra ret column
DataColumn^rt_col=gcnew DataColumn();
                     rt_col->ColumnName = "Ret";
                     rt_col->DataType=System::Type::GetType("System.Double");
                     dbdataset->Columns->Add(rt_col);
Then I need to fill the rows of this new column "Ret" based on the values held in "Population" column.
1st value of "Ret" should equal = log( 1st value of Population / 2nd value of Population)
2nd value of "Ret" = log (3rd value of Population / 4th value of Population)
....
 
ps: please let me reiterate that both "Ret" and "Population" are columns from the datable object dbdataset. 
 
Cheers
 
** in vba it will take me <3 minutes to perform it but I am stuck in c++ (part of the learning process I suppose ) Again thanks for the help