Random display

[Anon]

Im trying to get a random script working that displays 3 pictures from a group of 11, but when number 11 comes up its blank.

Can anyone have a look at the code and either advise how to optimise it?

$count_sql = "select * from portfolio";
$cresult = mysql_query($count_sql);
$count = mysql_num_rows($cresult);

// seed with microseconds since last "whole" second
srand((double)microtime()*1000000);

$random=(rand (1,$count));

$special_sql = "select * from portfolio where CLIENT=$random ";
$result = mysql_query($special_sql);

while ($portfolio = mysql_fetch_array($result)) {

echo "              <TR>";
echo "                  <TD align=middle>&nbsp;<BR>\n";
echo "                  <img src=\"img/screenshots/" . $portfolio["Image"] . "\" border=0  width=\"127\" height=\"126\">";
echo "                  </TD>";
echo "              </TR>";

}

[Anon]

Sorry, that last code was my playing bit - this is the code that is working but not effectivley

$count_sql = "select * from portfolio";
$cresult = mysql_query($count_sql);
$count = mysql_num_rows($cresult);

// seed with microseconds since last "whole" second
srand((double)microtime()*1000000);

$random=(rand (1,$count));

$special_sql = "select * from portfolio order by $random limit 3 ";
$result = mysql_query($special_sql);

while ($portfolio = mysql_fetch_array($result)) {

echo "              <TR>";
echo "                  <TD align=middle>&nbsp;<BR>\n";
echo "                  <img src=\"img/screenshots/" . $portfolio["Image"] . "\" border=0  width=\"127\" height=\"126\">";
echo "                  </TD>";
echo "              </TR>";

}

[Anon]

I'm not quite sure what you want to do with
order by $random limit 3

because you previously defined $random to be a value,
it's like ordering your results by 1 or by 3 or by 11

This does not order the results in a random way.
In MySQL 3.23 you could user "ORDER by Rand()"
Or you could create a semi-random set of images
by generating a number between 1 and (num_rows-2),
and using the offset command in mysql to start fetching results from 1-3 or 4-6 or 9-11
$random=(a_number_between_1_and_9)
select * from table where bla limit $random,3

[Anon]

$count_sql = "select * from portfolio";
mysql_num_rows($cresult);

this will load every thing you have to the memery.

i got a better way to doing this let the mysql return the number without loading to memery then calulate the total

change into:

$sql = "select count(ID) as num from portfolio";

$num = mysql_result($sql 0,'num');

try this.. much much more faster especically you have a huge database like 100K rows and this will save @!#$ load of memery..

but it seems doesn't work with Where statement on my machines......

vincent wrote:

I'm not quite sure what you want to do with
order by $random limit 3

because you previously defined $random to be a value,
it's like ordering your results by 1 or by 3 or by 11

This does not order the results in a random way.
In MySQL 3.23 you could user "ORDER by Rand()"
Or you could create a semi-random set of images
by generating a number between 1 and (num_rows-2),
and using the offset command in mysql to start fetching results from 1-3 or 4-6 or 9-11
$random=(a_number_between_1_and_9)
select * from table where bla limit $random,3