$link = mssql_connect('192.168.0.1', 'sa', 'passwd');
   mssql_select_db('base1', $link);

 $sql = "select *
  FROM OperatorConnections a
  join Operators b on a.Operator = b.Name
  where b.FullName = '" . $operator . "' and DATEDIFF (MI,dtBegin,dtEnd) > 5 and dtBegin > '" . $dat_query ."'";

echo $sql;  // Здесь вывожу текст запроса для проверки в MS

echo "<p>";

  $sql = mssql_query($sql);
 $len = mssql_num_rows ($sql);
 echo $len;


	mssql_close($link);

select * FROM OperatorConnections a join Operators b on a.Operator = b.Name where b.FullName = 'Иванова Светлана Вячеславовна' and DATEDIFF (MI,dtBegin,dtEnd) > 5 and dtBegin > '2013-03-01 00:00:00.000'