function db_field_value($TABLE_NAME,$FIELD_NAME,$DATABASE_NAME=''){
 if ($DATABASE_NAME!="") $DATABASE_NAME.=".";
 $sql="show create table ".$DATABASE_NAME.$TABLE_NAME;
 $rs=db_query($sql);
 $dl=mysql_fetch_row($rs);
 $sour=explode($FIELD_NAME,$dl[1]);
 $sour=explode("DEFAULT '",$sour[1]);
 $sour=explode("',",$sour[1]);
 return $sour[0];
}