Rand() help needed

[herghost]

Hi all,

 

Can someone explain and give me a quick example of how I would go about this?

 

I have 100 values in a database with  colum headings of t_val and t_name. If I wanted to update all 100 of these with a rand number how would I do this?

 

Would I do something like this?

t_val1 = rand(1,10);

 

What I want to do is have different variances in the rand as well. So ten would be rand(1,10) and the next ten would be rand(5,20) for example?

 

Many Thanks

[herghost]

Just re-read that and I am not sure how much sense it made so I will try again.

 

I have a table in my database that looks like this:

 

stock_id stock_name stock_desc stock_code t_val y_val

 

 

Now there is 100 rows in this table, with stock_id running from 5 to 104.

 

What I am trying to achieve is to update all these with a random value for t_val, while leaving the rest of the data intact.

 

I cant seem to get my head around how I would do this!

 

 

[severndigital]

I would pull the data first, then push the random number

 

this is the short version, since I don't know your mysql interface.

$array = "SELECT id FROM table";

for($i = 0; $i < count($array); $i++){
   $update = "UPDATE table SET t_val='" . rand(1,10) . "' WHERE id='" . $array[$i] ."'";
}

 

**EDIT **

this will NOT ensure that each entry gets a different random number, if that is needed.

[herghost]

Hi, thanks for the reply. Unfortunately they will all need a different random number :~(

 

Do you mind explaining what all the i++ business is as well? Not something I have come across before! Many thanks

[jonsjava]

increment by 1 (lets say $i=0 ; 0+1 = 1; 1+1=2;) For each increment through the loop, it adds one, until it meets the max (count($array))

[herghost]

ahhh thanks, that clears that one up

 

Any ideas on my original problem jonsjava?

 

Thanks to both of you for your help sp far

[herghost]

Would it be possible to do something like this?

 

Grab rows 5 to 15

enter into array value of t_val for these rows

count number of values

generate rand(1,10) for each value counted

replace values with rand output

update rows 5 to 15

 

Hmm, logically this makes sense to me, however its not within my skills in php even to know if its possible!

 

[jonsjava]

I've actually been working on an incrementing system for you.  Hopefully, something like this will do the job:

<?php
$array = "SELECT id FROM table";
$res = mysql_query($array);
for($i = 0; $i < count($res); $i++){
if (is_int($i/10) || $i == 0){
	$rand_low = rand(1,5);
	$rand_high = rand(10,20);
}
$num = rand($rand_low,$rand_high);
   $update = "UPDATE table SET t_val=$num WHERE id='" . $res[$i] ."'";
}

[herghost]

Many many thanks for your efforts

 

include('../common/dbconnect.php');

$array = "SELECT stock_id FROM stocks";
$res = mysql_query($array);
for($i = 0; $i < count($res); $i++){
   if (is_int($i/10) || $i == 0){
      $rand_low = rand(1,5);
      $rand_high = rand(10,20);
   }
   $num = rand($rand_low,$rand_high);
   $update = "UPDATE stocks SET t_val=$num WHERE stock_id='" . $res[$i] ."'";
}

 

This is what I am running in my browser to match up with my database details, however nothing happens! No errors and no update in the database? Am I missing something obvious here? This is far more advanced than the stuff I have been doing!

[jonsjava]

forgot to add this:

<?php
$array = "SELECT id FROM table";
$res = mysql_query($array);
for($i = 0; $i < count($res); $i++){
if (is_int($i/10) || $i == 0){
	$rand_low = rand(1,5);
	$rand_high = rand(10,20);
}
$num = rand($rand_low,$rand_high);
   $update = "UPDATE table SET t_val=$num WHERE id='" . $array[$i] ."'";
   if (mysql_query($update)){
   	echo "Updated $i record(s)<br />\n";
   }
}

[herghost]

thanks, get the message updated 0 records?! However, i have a row with an id of 0 which is meant to stay at a constant value of 2, however it is updating this but not rows 5+ etc!

[jonsjava]

Try this method:

<?php
$array = "SELECT id FROM table";
$res = mysql_query($array);
$count = 0;
while ($row = mysql_fetch_assoc($res)){
if (is_int($count / 10) || $count == 0){
	$rand_low = rand(1,5);
	$rand_high = rand(10,20);
}
$num = rand($rand_low,$rand_high);
$update = "UPDATE table SET t_val=$num WHERE id='" . $row['id'] ."'";
if (mysql_query($update)){
	echo "Updated $i record(s)<br />\n";
}
}

Change the querries to suit your schema.

[herghost]

Thanks, that updates them once I had removed the reference to $i,

 

Ill have a look at this and see if I can think of anything else to ask you! Many thanks for all your help

[jonsjava]

that was broken code I gave you. Sorry. Here's a fix:

<?php
$array = "SELECT id FROM table";
$res = mysql_query($array);
$count = 0;
while ($row = mysql_fetch_assoc($res)){
   if (is_int($count / 10) || $count == 0){
      $rand_low = rand(1,5);
      $rand_high = rand(10,20);
   }
   $num = rand($rand_low,$rand_high);
   $update = "UPDATE table SET t_val=$num WHERE id='" . $row['id'] ."'";
   $count++;
   if (mysql_query($update)){
      echo "Updated $count record(s)<br />\n";
   }
}