//（1）1对1

SqlDataAdapter da=new SqlDataAdapter("SqlString",SqlConnection);

da.fill(dataset,"tableName");

//（2）1对n

SqlDataAdapter da=new SqlDataAdapter("SqlString1",SqlConnection);

da.fill(dataset1,"tableName1");

//这里重新填充sql语句，填充对象可以使多个dataSet和dataTable。

da=new SqlDataAdapter("SqlString2",SqlConnection);

da.fill(dataset2,"tableName2");

//其他的情况类似，可以依次类推到第n张表或数据集。

//（3）n对n

SqlDataAdapter da1=new SqlDataAdapter("SqlString1",SqlConnection);

da1.fill(dataset1,"tableName1");

//这里重新填充sql语句，填充对象可以使多个dataSet和dataTable。

SqlDataAdapter da2=new SqlDataAdapter("SqlString2",SqlConnection);

da2.fill(dataset2,"tableName2");  

//数据库查询    DataSet 添加多张DateTable

SqlDataAdapter custAdapter = new SqlDataAdapter(

  "SELECT * FROM dbo.Customers", customerConnection);

OleDbDataAdapter ordAdapter = new OleDbDataAdapter(

  "SELECT * FROM Orders", orderConnection);

DataSet customerOrders = new DataSet();

custAdapter.Fill(customerOrders, "Customers");

ordAdapter.Fill(customerOrders, "Orders");

//--以下为应用

DataRelation relation = customerOrders.Relations.Add("CustOrders",

  customerOrders.Tables["Customers"].Columns["CustomerID"],

  customerOrders.Tables["Orders"].Columns["CustomerID"]);

foreach (DataRow pRow in customerOrders.Tables["Customers"].Rows)

{

  Console.WriteLine(pRow["CustomerID"]);

   foreach (DataRow cRow in pRow.GetChildRows(relation))

    Console.WriteLine("\t" + cRow["OrderID"]);

}

//---------------------------