I currently am using mysql and php to display 9 random results from my table of about 1100 records.
Would it be possible to have a next and previous button even though it's random? I looked at a couple of the examples already posted here but they seem to be application/project specific. Here is what my code looks like..
function executeQuery($searchKey)
{
if ($searchKey == null)
{
$query = "SELECT DISTINCT flightNumber, flightCity FROM allFlights LIMIT 0,9";
//DEBUG -echo "<p>$searchKey</p>";echo "<p>$query</p>";
}
else
{
//DEBUG -echo "<p>$searchKey</p>";echo "<p>var not null</p>";
$query = "Select distinct * from allFlights where flightCity LIKE '%$searchKey%' LIMIT 0,9";
//DEBUG -echo "<p>$searchKey</p>";echo "<p>$query</p>";
}
$result=mysql_query($query);
$numrow=mysql_numrows($result);
if ($numrow === 0)
{
$query = "Select distinct * from allFlights where flightNumber LIKE '%$searchKey%' LIMIT 0,9";
$result=mysql_query($query);
$numrow=mysql_numrows($result);
}
return $result;
}
function populate ()
{
$searchKey = mysql_real_escape_string($_POST["search"]); //assigns user input to searchKey variable
//DEBUG -echo "<p>$searchKey</p>";
$result=executeQuery($searchKey);
$numrow=mysql_numrows($result);
if ($numrow == 0)
{
echo "<center><p><b> No results found, please try another keyword.</p></center></b>";
}
else
{ display results. -- this part i have working.
}
I prefer upon loading the page this happens:
-The current position with respect to the # of flights available are listed. (Now showing 9 of 1100 flights)
-9 random flights are displayed.
-Next button that will show the next 9 flights (random would be nice.)
-Previous button that will show the previous(original) 9 flights (random would be nice.)
When all is said and done I would like to be able to load the page identify the 9 random flights, press next identify the new 9 random flights, then previous and identify the original 9 random flights.
Any help is much appreciated.
You can use ORDER BY RAND(seed) to give a pseudorandom order that is repeatable:
SELECT *
FROM ....
ORDER BY RAND(9325)
LIMIT 99, 9
Adjust the offset to move back and forwards through the results. The seed can be any integer, and you can change it if you want to re-randomize the order, but you must use the same seed when pressing back or forward.
Related
I have a reservation module in codeigniter wherein I limit users to reserve the clubhouse for only 2 hours a day. I am currently creating a validation in codeigniter to limit their reservation. What I did was to select all the reservations, and group them by the rows having the same date in order to properly limit them. The problem is that the model I created is only returning 1 row, and not all the results. This means that my counter is just being changed by only one row, which I expect that all rows should affect the counter.
Below is my database table:
Basically, the second row isn't supposed to be inserted in the database because user '20130123' already has used up his maximum reservation for the day which is two hours. I provided the validation check below on checking whether the user has used up two hours of reservation, and my logic here is that I just subtract the reservation end with the reservation start. Using the table above just as an example and for my explanation, my problem is that in my model, the counter's value becomes only "2" because it only reads the first row (8 - 6 = 2), instead of "3" (result of the first row which is 2, then add the result of second row which is 1 : [(8-6) + (9-8)])
To sum it up, my problem lies on the counter's value, because it is only being added by the first row the query reads.
Here's my code.
Model:
function check_twohours_clubhouse()
{
$query = $this->db->select('*')->from('clubhouse_reservation')->where('username', $this->session->userdata('username'))->group_by('reservation_date')->having('count(reservation_date) > 1')->get();
$result = $query->result();
if($query->num_rows() > 0)
{
$ctr = '0';
foreach($result as $row)
{
$totalhour = $row->reservation_end - $row->reservation_start; // subtract reservation start to reservation end to get the number of hours
$ctr = $ctr + $totalhour;
}
$ctr = $ctr + ($this->input->post('reserveend') - $this->input->post('reservestart')); // add the selected "add reservation" hours to the counter
if($ctr > 2) // counter > 2 hours limit
{
return FALSE;
}
else
{
return TRUE;
}
}
else
{
return TRUE;
}
}
Controller:
function create_reservation_clubhouse()
{
$this->form_validation->set_error_delimiters('<div class="error">','</div>');
$this->form_validation->set_rules('datepick', 'Date', 'required|no_olddate');
$this->form_validation->set_rules('reservestart', 'Reservation Start', 'required|hourselection|unique_reserve_clubhouse|max_twohours');
if ($this->form_validation->run() == FALSE)
{
$this->template->load('user_template', 'view_userreservation_addclubhouse');
}
else
{
if($this->model_reservation_user->check_twohours_courtone())
{
if($query = $this->model_reservation_user->create_reservation_clubhouse())
{
$this->session->set_flashdata('reservefeedback', 'You have successfully reserved a date for the Clubhouse. Please wait for the administrators to accept your reservation.');
redirect('user_reservation/clubhouse');
}
}
else
{
$this->session->set_flashdata('reservefail', 'You cannot reserve more than two hours of Clubhouse per day.');
redirect('user_reservation/clubhouse');
}
}
}
You can calculate all this in sql using time_to_sec() and timediff() functions:
select reservation_date, sum(time_to_sec(timediff(reserveend, reservestart)) / 3600 as reserved_hours
from clubhouse_reservation
where username =...
group by reservation_date
having count(*)>1 --although it is not clear to me why you have this restriction
The above query would sum up for a given user per reservation date, the hours for which the clubhouse is reserved (3600 = number of secs in an hour).
In your php code you only need to check if the reserved_hours in the resultset is >2 or not.
I'm not really an expert with CI, therefore I can't really tell how to convert the above sql to CI. But I'm afraid that you have to use raw sql because of the way it sums the time.
I have a query like this:
$sql = "SELECT * FROM doctors WHERE city ='$city' LIMIT 10 ";
$result = $db->query($sql);
And I show the result like this :
while($row = $result->fetch_object()){
echo $row->city;
}
The Problem :
Mysql , will search through my database to find 10 rows which their city field is similar to $city.
so far it is OK;
But I want to know what is the exact row_number of the last result , which mysql selected and I echoed it ?
( I mean , consider with that query , Mysql selected 10 rows in my database
where row number are:
FIRST = 1
Second = 5
Third = 6
Forth = 7
Fifth = 40
Sixth = 41
Seventh = 42
Eitghth = 100
Ninth = 110
AND **last one = 111**
OK?
I want to know where is place of this "last one"????
)
MySQL databases do not have "row numbers". Rows in the database do not have an inherent order and thereby no "row number". If you select 10 rows from the database, then the last row's "number" is 10. If each row has a field with a primary id, then use that field as its "absolute row number".
You could let the loop run and track values. When the loop ends, you will have the last value. Like so:
while($row = $result->fetch_object()){
echo $row->city;
$last_city = $row->city;
}
/* use $last_city; */
To get the row number in the Original Table of the last resultant (here, tenth) row, you could save the data from the tenth row and then, do the following:
1. Read whole table
2. Loop through the records, checking them against the saved data
3. Break loop as soon as data found.
Like So:
while($row = $result->fetch_object()){
echo $row->city;
$last_row = $row;
}
Now, rerun the query without filters:
$sql = "SELECT * FROM doctors";
$result = $db->query($sql);
$rowNumber = 0;
while($row = $result->fetch_object()) {
if($row == $last_row) break;
$rowNumber++;
}
/* use $rowNumber */
Hope this helps.
What you can do is $last = $row->id; (or whatever field you want) inside your while loop - it will keep getting reassigned with the end result being that it contains the value of the last row.
You could do something like this:
$rowIndex = 0;
$rowCount = mysqli_num_rows($result);
You'd be starting a counter at zero and detecting the total number of records retrieved.
Then, as you step through the records, you could increment your counter.
while ( $row = $result->fetch_object() ) {
$rowIndex++;
[other code]
}
Inside the While Loop, you could check to see whether the rowIndex is equal to the rowCount, as in...
if ($rowIndex == $rowCount) {
[your code]
}
I know this is a year+ late, but I completely why Andy was asking his question. I frequently need to know this information. For instance, let's say you're using PHP to echo results in a nice HTML format. Obviously, you wouldn't need to know the record result index in the case of simply starting and ending a div, because you could start the div before the loop, and close it at the end. However, knowing where you are in the result set might affect some styling decisions (e.g., adding particular classes to the first and/or last rows).
I had one case in which I used a GROUP BY query and inserted each set of records into its own tabbed card. A user could click the tabs to display each set. I wanted to know when I was building the last tab, so that I could designate it as being selected (i.e., the one with the focus). The tab was already built by the time the loop ended, so I needed to know while inside of the loop (which was more efficient than using JavaScript to change the tab's properties after the fact).
I have this script:
$rrezervim_id = rand(1, 5);
$result = mysql_query("SELECT rrezervim_id FROM pax_list WHERE rrezervim_id='$rrezervim_id'");
if(mysql_num_rows($result) == 1)
{
$rrezervim_id = rand(1, 5);
}
else(mysql_num_rows($result) > 1);
{
echo "$rrezervim_id";
}
What i am trying to do is To generate a Unique Random number using PHP and MySql
i have the value inside table( rrezervim_id)[Values:1,2,3,5] so the only Random number that have to be generated and is free is Number 4.
But with this script something is not working since i am getting even random that are already inserted in the table [Values:1,2,3,5].
Any one can help me, is very important to make a check in mysql before generating the unique number if already exist in table.
First of all, the direct error in your code is
if(mysql_num_rows($result) == 1)
{
$rrezervim_id = rand(1, 5);
}
fails, if you hit a taken number twice. You need a loop, such as
while (mysql_num_rows($result) == 1)
{
$rrezervim_id = rand(1, 5);
$result = mysql_query("SELECT rrezervim_id FROM pax_list WHERE rrezervim_id='$rrezervim_id'");
}
That said, I suspect, that there is more wrong with your code:
If you want to use this "free" random number to insert it into the database at a later point in time, you are wide open to a race condition: Both processes select the same (still free) number, but only on the first insert is it still unique.
This approach can have extremely bad performance, if your field of possible random numbers is nearly full: If you have 80% fill rate, such as in your example, you will on average have 4 "bad" hits, before getting a "good" hit.
I recommend you consider using a database built-in, such as the battle-proven AUTO_INCREMENT as a primary means, then use a formula to create the hard-to-guess pseudo-random from it. A linear feedback shift register can be one approach, while cryptographically combining the auto-generated ID and a (not necessarily unique) pseudo-random stored in the table might be another. Both methods give you linear performance and race-free usage.
you can create unique number in php
<?php
echo uniqid();
?>
But you should use AUTO INCREMENT. If you want to know by which number inserted item is saved use something like this:
function insertUser(){
Global $userName;
$sqlInsert="INSERT INTO person (e_mail)
VALUES ('".$userName."')";
if (!mysql_query($sqlInsert)){
die('Error: ' . mysql_error());
}
$userId = mysql_insert_id();
return $userId;
}
in $userId is last inserted value
Since you are not using AUTO_INCREMENT, a suggestion (which is slow) is to select all the numbers that are valid and pick 1 randomly.
If we have [1,2,3,5,7] and our allowed elements are 1..10, then we have 5 allowed elements(4,6,8,9,10). So we rand(1,5). If we get "1", our next number is 4, if we get "2", our next number is 6. To better explain the idea:
Rand(1,5) Our array Value(available)
1
2
3
1 - 4
5
2 - 6
7
3 8
4 9
5 10
Code example:
$max_num = 100;
$res = mysql_query("SELECT rrezervim_id FROM pax_list ORDER BY rrezervim_id ASC");
$nums = [];
while($row = mysql_fetch_assoc($res)){
$nums[] = $res['rrezervim_id'];
}
$numbers_allowed = $max_num - count($nums); // actual number of allowed elements
$new_num_idx = rand(1, $numbers_allowed); // The selected element's index
(skipping all existing elements)
// in the following loop: $j starts as our lowest options.
// when $new_num_idx reaches 0 - it means that we have skipped
// over $new_num_idx elements. The next available element is
// our choice. $new_num_idx is a countdown
for($i=0,$j=1, $n=count($nums); $i<$n && $new_num_idx > 0; $i++){
while ($nums[$i]>$i+$j){
$j++; $new_num_idx--;
}
}
return $i+$j;
I need to get a random number between, lets say 1-200, but at the same time I need to prevent selecting a random number that has already been used for a particular REMOTE_ADDR (as stored in a table).
This is what I have so far (I have tried several different approaches):
$ip = $_SERVER['REMOTE_ADDR'];
$query7 = "
SELECT *
FROM IP
WHERE IP = '$ip'
";
$result7 = mysql_query($query7) or die(mysql_error());
$rows7 = mysql_num_rows($result7);
while ($row7 = mysql_fetch_array($result7)){
$id = $row7['ID'];
}
I'm using the random number to pick an image to display, but my users are complaining that the images selected for them is not random enough; ie, the same picture is getting "randomly" selected too often, sometimes showing the same image over and over.
It does not have to be in PHP, if there is another option.
Something like that
// all ids from 1 to 100
$all = array_fill(1, 200, 0);
// remove used
foreach ($used as $i) {
unset($all[$i]);
}
// get survived keys
$keys = array_keys($all);
// get random position, note that the array with keys is 0 based
$j = rand(0, count($all) - 1);
return $keys[$j];
Run your select and instead of using *, only select the id column. Then use:
while($row7[] = mysql_fetch_array($query7));
do{
$rand = rand(0,200);
}while(in_array($rand,$row7));
You can do it all in mysql. Have one table that has your list of images, and another table that has the list of IP addresses and the images that have already been shown to that IP. Then you select and join the tables and order the result randomly.
SELECT image_id FROM images
LEFT JOIN shown_images ON images.image_id=shown_images.image_id AND ip_addr=[#.#.#.#]
WHERE shown_images.image_id IS NULL
ORDER BY RAND() LIMIT 1;
After you show an image to an IP, just insert a record into the shown_images table with the IP and the image ID. That will work right up until that have seen all the images. Then you can delete the records and start over.
This answer assumes that you have 200 items, and collect the items which you do not want to show. Alternatively, you can query only id's of available items and choose from these, you would need to create a table with available items for that.
Create a map which maps consecutive numbers to (non-consecutive) available numbers. Suppose the numbers 1 and 3 are in use, you can map to 2 and 4 (and so on).
Actually, it is possible to use a simple array (not-associative) for this. You can do something like this:
$reserved = array(1, 3); // fill $reserved using your code
$available = array();
for ($i = 1; $i <= 200; $i++) {
if (!in_array($i, $reserved)) {
$available[] = $i;
}
}
if (count($available) > 0) {
$random_index = rand(0, count($available) - 1);
$r = $available[$random_index];
} else {
// Nothing available!
}
There will be nothing to choose when you run out of pictures that have not been displayed yet. In this case, count($available) will be zero. One way to solve this would be to clear your list of displayed images for the current IP and choose again; see also other answers for this.
This is part of code from my backoffice page. ( is an edit.php page for a user to edit / modify )
// first query to get cats from user table
$query = "select * from user where name='".$_SESSION['username']."' order by id ASC limit 1";
$result=mysql_query($query);
if (mysql_num_rows($result)) {
while($row=mysql_fetch_array($result)){
$cat1 = $row['cat1'];
$cat2 = $row['cat2'];
$cat3 = $row['cat3'];
$cat4 = $row['cat4'];
$cat5 = $row['cat5'];
$cat6 = $row['cat6'];
$cat7 = $row['cat7'];
$cat8 = $row['cat8'];
$cat9 = $row['cat9'];
$cat10 = $row['cat10'];
}
}
// now i want to build 10 select boxes with selected according the user table $cats
// below is what i can build to first box $cat1
// is there a way i can produce this for the 10 select boxes whitout having to make 10 cycles of bellow code
<select name="theme" id="theme">
<?php
$q1 = 'SELECT * FROM cats ORDER BY title ASC';
$r1 = mysql_query($q1);
while( $row = mysql_fetch_array($r1)) {
if ( $cat1 == $row['id'] ) {
print "<option class=\"cssoption\" selected=\"selected\" value=\"".$row['id']."\">".htmlentities($row['title'])."</option>";
}
else {
print "<option class=\"cssoption\" value=\"".$row['id']."\">".htmlentities($row['title'])."</option>";
}
}
?>
</select>
I am not a coder so this might not be effective code.
Hope someone can help me here and understands what i am trying to do.
Many Thanks.
The code is fine. This 10 cycles as you name it is a almost zero cost.
This is the usual way we do it, we fetch sequentialy the records one by one.
In addition it makes no sense to ask not to do the 10 cycles because you are applying an if else condition in the same time, this means that you check every record if the cat id is the same with the row so you need the loop.
On the other hand if for some reason you want to skip some records, you can use the mysql seek function to start fetching from the desired record.
for($i=0;$i<99999;$i++)
(9999*9999);
echo 'This time the cost of this loop was:',(microtime()-$start),' seconds.';
?>