找出前後三天中的資料

找出前後三天中的資料，我是這樣想的

$squery_1 ="select * from Agent_tbl where ((to_days(now())-to_days(ETime)<=3 and to_days(now())-to_days(ETime)>=0) or (to_days(STime)-to_days(now())<=3 and to_days(STime)-to_days(now())>=0)) and PId='$rows[PId]'";

$ssql_1   =mysql_query($squery_1) or die($squery_1);
$num_1    =mysql_num_rows($ssql_1);
$row_1    =mysql_fetch_array($ssql_1);