Leia várias tabelas com relações com t-sql no DataSet

SQL = "SELECT table1.x, table2.z FROM table1 
       INNER JOIN table2 ON table1.ID = table2.SubID
       FOR XML AUTO, XMLDATA";

DataSet data = new DataSet();
DbCommand cmd = conn.CreateCommand();
cmd.CommandText = SQL;
data.ReadXml(((System.Data.SqlClient.SqlCommand)cmd).ExecuteXmlReader(),
               xmlReadMode.Fragment);