windows form Parent and child in one datagridiew

My Question is i have stock item table {item no, item name } and purchase child table include { item no}, i want to have datagridview have item no from purchase child and when select item it show the item name directly. have a relation between parent and child.

i used this code but i am not convinced ;

private string selectQueryStringPurChild = "SELECT dbo.acc_PurChild.iRecnoPur, dbo.acc_PurChild.iPurchaseID, dbo.acc_PurChild.iStockID, " +
"dbo.acc_Stkitem.cFullname, dbo.acc_PurChild.nQty, dbo.acc_PurChild.nDisc, dbo.acc_PurChild.nCost, " +
"dbo.acc_PurChild.nTotal, dbo.acc_PurChild.nVat, dbo.acc_PurChild.nLine " +
"FROM dbo.acc_PurChild INNER JOIN " +
"dbo.acc_Stkitem ON dbo.acc_PurChild.iStockID = dbo.acc_Stkitem.iStockID";

private void dgvacc_PurChild_CellLeave(object sender, DataGridViewCellEventArgs e)
{
int ncolumn = dgvacc_PurChild.CurrentCell.ColumnIndex;
switch (ncolumn)
{
case 1:
GetStockItemFullName();
break;
}
}

private void GetStockItemFullName()
{
dgvacc_PurChild.CurrentRow.Cells[2].Value = "2222";
}