Random function problem

[javierccs]

hello,

im having trouble with the random function on a page, its selecting only the first register of the select

$rsmotd = mysql_query("select count(idmotd) motdct from motd where idmotd in (16,17,18)", $conn);
  $rowsmotd = mysql_fetch_array($rsmotd);
  // Making the Random process using the count used before
  $radnmod = rand(1,$rowsmotd["motdct"]);
  // Selecting the Random MOTD
  $rsmotd = mysql_query("select * from motd where idmotd in (16,17,18)", $conn);
  $rowsmotd = mysql_fetch_array($rsmotd); 

i cant seem to find the problem but right now its just showing the motd wich id number is 16

please, little help over here.....!!!!

[Drinky]

mysql_fetch_array() fetches the first row of the result set and moves the pointer to the next row, a subsequent call to mysql_fetch_array() will return the second row and so forth. Because you only ever call it once you will only ever get the first row of the result.

I can't see where you use the variable $radnmod in this code slice, which you get from the rand() funtion. NOTE: that in php versions prior to 4.2.0 you need to seed the rand() function with srand() before calling rand() otherwise you will get the same random number sequence each time.

For your code to work you would need to return the result set into an array and pick the index using your random number.

// your code here
 
while($aRow = mysql_fetch_array($rsmotd)){
    $aResult[] = $aRow;
}
 
$aRandomRow = $aResult[$radnmod]; 

However this is somewhat inefficient (and will get worse as the number of rows in your table increase), you could use the MySQL SQL Limit statement to return your 1 random row.

$rsmotd = mysql_query("select count(idmotd) motdct from motd where idmotd in (16,17,18)", $conn); 
$rowsmotd = mysql_fetch_array($rsmotd); 
// Making the Random process using the count used before 
//$radnmod = rand(1,$rowsmotd["motdct"]); 
 
$radnmod = rand(0,$rowsmotd["motdct"]-1); 
 
// Selecting the Random MOTD 
// $rsmotd = mysql_query("select * from motd where idmotd in (16,17,18)", $conn); 
// $rowsmotd = mysql_fetch_array($rsmotd);
 
// Pick just one row from the table
$rsmotd = mysql_query("select * from motd where idmotd in (16,17,18) LIMIT $radnmod,1", $conn);
$rowsmotd = mysql_fetch_array($rsmotd); 

[javierccs]

sorry man, it doesnt work
and it gives me this error
Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /home/httpd/html/index.php on line 17

this is line 17

$rowsmotd = mysql_fetch_array($rsmotd); 

the problem starts because i have a 15 register table (motd) and i used the random function to selected one to show randomly,

then i added 3 registers this morning, and i want to just select randomly these 3 new registers, this is the code i used for the 15 register table, it works ok

$rsmotd = mysql_query("select count(idmotd) motdct from motd ", $conn);
  $rowsmotd = mysql_fetch_array($rsmotd);
  // Making the Random process using the count used before
  $radnmod = rand(1,$rowsmotd["motdct"]);
  // Selecting the Random MOTD
  $rsmotd = mysql_query("select * from motd where idmotd='$radnmod'", $conn);
  $rowsmotd = mysql_fetch_array($rsmotd);