DateSet

DateSetusing System;
using System.Data;
using System.Data.SqlClient;namespace _09_09
{
class Class_09_09
{
  public static void Main(String[] args)
  {
   DataSet ds = new DataSet();
   ds.ReadXml("StudentsAddress.xml");   ds.WriteXmlSchema("StudentsAddress.xsd");   foreach(DataTable t in ds.Tables)
   {
    Console.WriteLine("{0} 表", t.TableName);
    foreach(DataColumn c in t.Columns)
    {
     Console.Write("\t{0}", c);
    }
    Console.WriteLine();
    foreach(DataRow r in t.Rows)
    {
     for(int i = 0; i < t.Columns.Count; ++i)
      Console.Write("\t{0}", r[i]);     Console.WriteLine();
    }
   }   foreach(DataRelation r in ds.Relations)
   {
    Console.WriteLine("关系 {0}: ", r);
    Console.WriteLine("\tParentTable: {0}", r.ParentTable);
    Console.WriteLine("\tParentColumn: {0}", r.ParentColumns[0]);  
    Console.WriteLine("\tChildTable: {0}", r.ChildTable);
    Console.WriteLine("\tChildColumn: {0}", r.ChildColumns[0]);
   }
  }
}
}
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    Console.WriteLine("\tParentColumn: {0}", r.ParentColumns[0]);  
Console.WriteLine("\tChildColumn: {0}", r.ChildColumns[0]);
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ChildColumns[0]);
ParentColumns[0]);  
这是什么意思？？括号里的0代表哪一列。是什么意思