My page displays an image, and I want to display the previous and next image that is relevant to the current one. At the moment I run the same query 3x and modify the "where" statement with =, >, <.
It works but I feel there must be a better way to do this.
The image id's are not 1,2,3,4,5. and could be 1,2,10,20,21 etc. But if it is much more efficient I am willing to change this.
mysql_select_db("database", $conPro);
$currentid = mysql_real_escape_string($_GET['currentid']);
$query ="SELECT * FROM database WHERE id ='".$currentid."' LIMIT 1 ";
$result = mysql_query($query,$conPro) or die(mysql_error());
$affected_rows = mysql_num_rows($result);
if ($affected_rows==1)
{
$row = mysql_fetch_array($result)or die ('error:' . mysql_error());
$current_id = $row['id'];
$current_header = $row['title'];
$current_description =$row['desc'];
$current_image = "http://".$row['img'];
$current_url = "http://".$row['id']."/".$db_title."/";
$current_thumb = "http://".$row['cloud'];
}
mysql_select_db("database", $conPro);
$query ="SELECT * FROM database WHERE id <'".$currentid."' ORDER BY id DESC LIMIT 1 ";
$result = mysql_query($query,$conPro) or die(mysql_error());
$affected_rows = mysql_num_rows($result);
if ($affected_rows==1)
{
$row = mysql_fetch_array($result)or die ('error:' . mysql_error());
$previous_id = $row['id'];
$previous_header = $row['title'];
$previous_description =$row['desc'];
$previous_image = "http://".$row['img'];
$previous_url = "http://".$row['id']."/".$db_title."/";
$previous_thumb = "http://".$row['cloud'];
}else{
$previous_none = "true"; //no rows found
}
mysql_select_db("database", $conPro);
$query ="SELECT * FROM database WHERE id >'".$currentid."' ORDER BY id ASC LIMIT 1 ";
$result = mysql_query($query,$conPro) or die(mysql_error());
$affected_rows = mysql_num_rows($result);
if ($affected_rows==1)
{
$row = mysql_fetch_array($result)or die ('error:' . mysql_error());
$next_id = $row['id'];
$next_header = $row['title'];
$next_description =$row['desc'];
$next_image = "http://".$row['img'];
$next_url = "http://".$row['id']."/".$db_title."/";
$next_thumb = "http://".$row['cloud'];
}else{
$next_none = "true"; //no rows found
}
mysql_close($conPro);
Thank you for your time
You don't have to do select_db each time. Once you 'select' a db, it stays selected until you select something else.
You can't really get away from doing two separate queries to get the next/previous images, but you can fake it by using a union query:
(SELECT 'next' AS position, ...
FROM yourtable
WHERE (id > $currentid)
ORDER BY id ASC
LIMIT 1)
UNION
(SELECT 'prev' AS position, ...
FROM yourtable
WHERE (id < $currentid)
ORDER BY id DESC
LIMIT 1)
This would return two rows, containing a pseudofield named 'position' which will allow you to easily identify which row is the 'next' record, and which is the 'previous' one. Note that the brackets are required so that the 'order by' clauses apply to the individual queries. Without, mysql will take the order by clause from the last query in the union sequence and apply it to the full union results.
You can get the "previous" one first WHERE id <'".$currentid."' ORDER BY id DESC, and then query for two "above" it: SELECT * FROM database WHERE id >= '".$currentid."' ORDER BY id ASC then it takes only two queries instead of three.
Related
I'm trying to fetch random column from database using Rand() function.
It's returning random value but many time it is returning duplicate.
This is what my database table look like.
Column
Type
Null
Default
no
int(30)
No
postid
varchar(100)
Yes
NULL
byuser
varchar(32)
Yes
NULL
likeslimit
int(30)
No
createdon
date
No
And this is what my PHP code is.
$query = mysqli_query(
$mysql,
"SELECT postid FROM history ORDER BY Rand() LIMIT 1"
);
if (mysqli_num_rows($query) == 1) {
while ($row = mysqli_fetch_assoc($query)) {
echo $row['postid'];
}
}
I want it to always return random never the same till the end of data reached.
Don't use loop and condition you want only 1 limit try this
$query = mysqli_query(
$mysql,
"SELECT postid FROM history ORDER BY Rand() LIMIT 1"
);
$row = mysqli_fetch_assoc($query)
echo $row['postid'];
This is the way RAND in mysql works and will repeat the results from time to time. But you can achieve such functionality by using mysql with php.
$query = mysqli_query($mysql, "SELECT postid FROM cacheTable WHERE 1 ORDER BY RAND() LIMIT 1");
$row = mysqli_fetch_assoc($query);
$foundId = (int)$row['postid'];
if((int) $foundId === 0) { // NO records left in cacheTable then fill it up again
mysqli_query($mysql, "INSERT INTO cacheTable (postid) SELECT postid FROM history");
$query = mysqli_query($mysql, "SELECT postid FROM cacheTable WHERE 1 ORDER BY RAND() LIMIT 1");
$row = mysqli_fetch_assoc($query);
$foundId = (int) $row['postid'];
}
mysqli_query($mysql, "DELETE FROM cacheTable WHERE postid=".$foundId); // DELETE the record
$query = mysqli_query($mysql, "SELECT * FROM history WHERE postid=".$foundId);
$result = mysqli_fetch_assoc($query);
cacheTable will have only one column - ID (primary key) which will hold the corresponding ID (primary key) from history. cacheTable structure:
|------
|Column|Type|Null|Default
|------
|postid|varchar(100)|Yes|NULL
|-----
cacheTable will fill with all the ids from history table (it will be done once the cacheTable is empty). You will select rand result from the cacheTable and you will delete it then so it will not appear in the next selects. When we are out of records in cache table it will populate again.
NB: this approach has one major drawback - when you have new entries in history table they won't be available in cache table until it is empty and filled again.
This is the code Samir Nabil Suggested :
session_start();
$_SESSION['dupes'] = array();
$query = mysqli_query(
$mysql,
"SELECT postid FROM history ORDER BY Rand() LIMIT 1"
);
if (mysqli_num_rows($query) == 1) {
while ($row = mysqli_fetch_assoc($query)) {
if (!in_array($row['postid'], $_SESSION['dupes'])) {
echo $row['postid'];
$_SESSION['dupes'][] = $row['postid'];
}
}
}
Hopefully this will be quite simple for someone.
I have the following code:
<?php
// Connects to your Database
mysql_connect("localhost", "xxxxx", "xxxxx") or die(mysql_error());
mysql_select_db("xxxxx") or die(mysql_error());
require("../includes/common.php");
require("admin_header.php");
require("admin_menu.php");
$query = "Truncate TABLE pt_menutitles";
$result = mysql_query($query) or die(mysql_error());
// Menu Headers for Category
$data = "select a.menuheader, a.total from(SELECT distinct (menuheader),count(*) as total FROM `pt_products` WHERE `menuheader` <> '' group by `menuheader` order by total desc limit 4) a order by a.menuheader";
$result = mysql_query($data) or die(mysql_error());
while($info = mysql_fetch_array($result))
{
$menudata = "select a.subcategory, a.menuheader,a.totcount FROM(SELECT distinct (subcategory),menuheader,count(*) as totcount FROM `pt_products` WHERE `menuheader`='".$info['menuheader']."' AND subcategory <> ''group by `subcategory` order by totcount desc limit 4) a order by a.subcategory";
$menuresult = mysql_query($menudata) or die(mysql_error());
while($menuinfo = mysql_fetch_array($menuresult))
{
$sql = "Insert into pt_menutitles (menu, title, totalcount) select '".$menuinfo['menuheader']."','".$menuinfo ['subcategory']."','".$menuinfo ['totcount']."'";
$result = mysql_query($sql) or die(mysql_error());
}
}
?>
Basically I take the top 4 menu titles that have the most items in them, then select the top 4 subcategories in them titles and insert them into a table.
What is happening though is that i'm onlyt getting Menu Title 1 and Subcategories 1 to 4 inserted into my table.
It's as though the the loop is ending after the first time round?
Any advise would be great!
Cheers
Chris
This line replaces your existing result and ends the loop. Use any other (non-existing) variable name, but not $result.
$sql = "Insert into pt_menutitles (menu, title, totalcount) select '".$menuinfo['menuheader']."','".$menuinfo ['subcategory']."','".$menuinfo ['totcount']."'";
$result = mysql_query($sql) or die(mysql_error());
I'm not sure exactly how to explain what the query does, however the problem isn't entirely with how it's set up, because it does work, in another instance, when I use it as an array, however it's not working when I use it with mysql_fetch_assoc(), so here is what my original query is(not the one im having trouble with):
SELECT * FROM
(SELECT * FROM comments
WHERE postID='$id' AND state='0'
ORDER BY id DESC LIMIT 3
) t ORDER BY id ASC
what this does is selects the last 3 comments on a post, then orders them in another way (so they show up in the correct order, old to new) Now this is the query for echoing out the array of comments directly.
But now what I want to do, is to just get the first id out of the 3 comments.
here's what I have tried to do (and by the way, this query DOES work, when i replace my previous query to echo out the results in an array, but i need to get just the id for use, i don't want an array):
$previousIDq = mysql_fetch_assoc(mysql_query("
SELECT * FROM
(SELECT * FROM comments
WHERE postID='$id' AND state='0'
ORDER BY id DESC LIMIT 3
) t ORDER BY id ASC LIMIT 1"));
$previousID = $previousIDq['id']; //this doesn't return the id as I want it to.
Your problem may be that there are no matching rows.
Also, I think you could also improve your query to this:
SELECT * FROM comments WHERE postID='$id' AND state='0' ORDER BY id DESC LIMIT 2,1
But as others say, use PDO or MySQLi, and with prepared statements. And don't SELECT * ever.
try a var_dump($previousID) to see what you get
It is probably giving you back an object, and you need to get your id from that object
You script is too condensened for error handling, let alone debugging
$mysql = mysql_connect(...
$query = "
SELECT * FROM
(SELECT * FROM comments
WHERE postID='$id' AND state='0'
ORDER BY id DESC LIMIT 3
) t ORDER BY id ASC LIMIT 1
";
$result = mysql_query($query, $mysql);
if ( !$result ) { // query failed
die('<pre>'.htmlspecialchars(mysql_error($mysql)).'</pre><pre>'.htmlspecialchars($query).'</pre>');
}
$previousIDq = mysql_fetch_assoc($result);
if ( !$previousIDq ) {
die('empty result set');
}
else {
$previousID = $previousIDq['id'];
}
You need to separate your code to be able to debug
$query = "SELECT * FROM
(SELECT * FROM comments
WHERE postID='$id' AND state='0'
ORDER BY id DESC LIMIT 3
) t ORDER BY id ASC LIMIT 1";
$result = mysql_query($query);
echo mysql_error(); //what eror comes out here
while($previousIDq = mysql_fetch_assoc($result))
{
print ($previousIDq['id']);
}
NOTE: mysql_* is depreciated, upgrade to mysqli or PDO
Please stop using mysql_ functions to write new code, it is being deprecated. Use mysqli_ or PDO functions (mysqli below).
Bind your parameters to prevent SQL injection
Always use a column list (don't use SELECT *)
If you're returning > 1 row, use a while loop
mysqli_ solution
$link = mysqli_connect("localhost", "user_name", "password", "stock");
if (mysqli_connect_error()) {
die('Connect Error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error());
}
$stmt = mysqli_prepare($link, "SELECT t.id FROM
(SELECT id FROM comments
WHERE postID = ? AND state = 0
ORDER BY id DESC
LIMIT 3) t
ORDER BY id ASC");
mysqli_bind_param($stmt, 's', $id) or die(mysqli_error($dbh));
$result = mysqli_stmt_execute($stmt) or die(mysqli_error($link));
while($row = mysqli_fetch_assoc($result)) {
echo $row[id];
}
mysqli_close($link);
mysql_ solution
$stmt = "SELECT t.id FROM
(SELECT id FROM comments
WHERE postID = $id AND state = 0
ORDER BY id DESC
LIMIT 3) t
ORDER BY id ASC";
$result = mysql_query($stmt) or die(mysql_error());
$row = mysql_fetch_assoc($result);
while($row = mysql_fetch_assoc($result)) {
echo $row[id];
}
I have the following code:
$query = mysql_query("SELECT * FROM activity ORDER BY activity_time DESC LIMIT 50");
while($result = mysql_fetch_array($query)) {
extract($result);
if ($activity_type == "discussion") {
$query = mysql_query("SELECT * FROM discussions WHERE discussion_uuid = '$activity_ref'");
while($result = mysql_fetch_array($query)) {
extract($result);
echo $discussion_user . " said:<br>" . $discussion_text . "<br>";
}
} elseif ($activity_type == "file") {
}
}
But it just returns the last row. My goal is to have a chronological list of "activities" each displayed slightly differently depending on their type.
Your using $query and $result twice so the second loop is overwriting the result of the first and stopping...
$query = mysql_query("SELECT * FROM activity ORDER BY activity_time DESC LIMIT 50");
and
$query = mysql_query("SELECT * FROM discussions WHERE discussion_uuid = '$activity_ref'");
same with $results var...
I would suggest you change to $query and $query2 but best to use something like
$activies = mysql_query("SELECT * FROM activity ORDER BY activity_time DESC LIMIT 50");
while($activity = mysql_fetch_array($activies)) {
and
$discussions = mysql_query("SELECT * FROM discussions WHERE discussion_uuid = '$activity_ref'");
while($discussion = mysql_fetch_array($discussions)) {
I would also avoid using extract - as you might be overwriting vars your not expecting to...
You have to create another connection to the database so that you can run them at the same time.
OR
You can load the results of the first one into an array, and then just loop through the array.
I have the following PHP functions that determine the next and previous rows in a database. However, there are lots of occasions when rows can be deleted and therefore my functions will not work as all they do is decrement the auto_increment field.
For example, current row 5. My function gives: 4 (previous) and 6 (next). What if 6 and 7 is deleted. My best idea is to keep querying until I get a row, but this seems inefficient, is there a better way?
Thanks all
//function to get next tweet
function getNextTweet($key, $direction){
$sql = "SELECT tweet_id FROM tweets WHERE tweet_key = '$key' LIMIT 1";
$result = mysql_query($sql) or die("DB Error : ". mysql_error());
$result = mysql_fetch_assoc($result);
if($direction=='next'){
$tweet_id = $result['tweet_id'] + 1;
}else{
$tweet_id = $result['tweet_id'] - 1;
}
$sql = "SELECT * FROM tweets WHERE tweet_id = '$tweet_id' LIMIT 1";
$result = mysql_query($sql) or die("DB Error : ". mysql_error());
return mysql_fetch_assoc($result);
}
Assuming you don't have a bajillion records...
Previous:
SELECT *
FROM table
WHERE (id < currentID)
ORDER BY id DESC
LIMIT 1
Next
SELECT *
FROM table
WHERE (id > currentID)
ORDER BY id ASC
LIMIT 1
If you run a modern version of MySQL, you can simplify your function into
function getNextTweet($key, $direction)
{
$cmp = ($direction == 'next') ? '>' : '<';
$order = ($direction == 'next') ? 'ASC' : 'DESC';
$sql = "SELECT *
FROM tweets
WHERE tweet_id $cmp (SELECT tweet_id FROM tweets WHERE tweet_key = '$key' LIMIT 1)
ORDER BY tweet_id $order
LIMIT 1";
$result = mysql_query($sql) or die("DB Error : ". mysql_error());
return mysql_fetch_assoc($result);
}
As long as "tweet_id" is indexed, the query will be very fast, even for millions of records.
One last thing, make sure that $key is properly validated! Otherwise, anyone can inject SQL in your query, that's a huge security flaw. If $key is anything but a hash key, it should at least go through mysql_real_escape_string()