i want to write a MySql function that the Limit is set by a row on the table called.
Let me explain.
$query=mysqli_query($this->db,"SELECT a_row, b_row, c_row FROM table WHERE a_row='something' ORDER BY 'whatever' **LIMIT 'c_row'** DESC")or die(mysqli_error($this->db));
c_row in an integer number on the db.
I tried to make a variable before calling the $query from the row (c_row) but i dont think thats possible.
You can use a sub-query to access the value of c_row and use it for the LIMIT clause.
$query=mysqli_query($this->db,"SELECT a_row, b_row, c_row FROM table
WHERE a_row='something' ORDER BY 'whatever' LIMIT (SELECT c_row from table) DESC")or die(mysqli_error($this->db));
Related
Guys am trying to select the top/recently third row, i tried this one but it doesn't work, where do i make mistake ?
<?php
$sql = "SELECT * FROM songs ORDER BY id ASC LIMIT 1,2;";
$result = mysqli_query($con, $sql);
$resultCheck = mysqli_num_rows($result);
if (mysqli_num_rows($result) > 0) {
while ($row = mysqli_fetch_assoc($result)) {
echo $row['artist'];
}
}
?>
Use OFFSET:
SELECT * FROM songs ORDER BY id ASC LIMIT 1 OFFSET 2
The shorthand (which you are using) is reversed, so OFFSET is first then LIMIT:
SELECT * FROM songs ORDER BY id ASC LIMIT 2,1;
Use OFFSET
Here the limit 1 It simply means and you need one record
and the offset means skip the first 2
SELECT * FROM songs ORDER BY id ASC LIMIT 1 OFFSET 2
The parameters you use after limit should be reversed.
The first parameter is offset, and the second parameter is number of record you want.
SELECT * FROM songs ORDER BY id ASC LIMIT 2,1
This is just my opinion--
Sorting like this should always be done in client software.
Extract the data - remove the ORDER BY for your SQL...
Sort it in your client, and select and return the third line to the caller.
You will get better scalability and maintainability than driving all of this through an SQL query.
This is my go-to approach when solving these types of problems through custom software and it has been proven out over time.
Think about this:
Select ID from songs
get the id's into your code, and sort them there. Then chose the third one in the list. Then:
select title, author, artist, ... from songs where ID = VALUE FROM ID ABOVE
Yes, you are hitting the database twice, but these are two very efficient queries and that will perform better as your database scales, than the fancy order by you propose.
$active_sth = $dbh->prepare("SELECT * FROM user_campaign
WHERE status='blasting'
OR status='ready'
OR status='followup_hold'
OR status='initial_hold'
AND uid=:uid
ORDER BY status ASC");
$active_sth->bindParam(':uid', $_SESSION['uid']['id']);
$active_sth->execute();
I am positive $_SESSION['uid']['id'] = 7
but it will also pull results of id 10 or any other number.
Is my AND/OR clause written wrong?
Yes, query is wrong
SELECT * FROM user_campaign
WHERE (
status='blasting'
OR status='ready'
OR status='followup_hold'
OR status='initial_hold'
)
AND uid=:uid
ORDER BY status ASC
You have to group all ORs to make sure that row got one of this values, and separately check if it have given uid.
The proper way to write that is:
SELECT * FROM user_campaign
WHERE status IN ('blasting', 'ready', 'followup_hold', 'initial_hold')
AND uid =: uid
ORDER BY status ASC
You should use IN instead of that huge amount of ORs :)
i have following sql query, everything works fine but when i put "and posted_date<>$datetime" its not retrieving data as per given command.
$datetime="0000-00-00";
$data = mysql_query("SELECT * FROM product_table where category_id=$cat1 or
pid=$par or gpid=$gpar and posted_date<>$datetime
ORDER BY autoid desc limit $no2,$cacount")
or die(mysql_error());
please check is that line is ok maybe i am doing mistake somewhere where category_id=$cat1 or pid=$par or gpid=$gpar and posted_date<>$datetime
maybe i need two where one for or and another for and...
Thanks
Try to group your condition and use DATE()
SELECT *
FROM product_table
where (category_id=$cat1 or
pid=$par or gpid=$gpar) AND DATE(posted_date) <> DATE($datetime)
ORDER BY autoid desc
LIMIT $no2, $cacount
I am running an mysql query and I am trying to order the results by there auto incrementing index value. I am running my query with this code.
$query = mysql_query("SELECT * FROM chanels WHERE videolocation != '' ORDER BY index DESC ");
This worked before I added the ORDER BY function and now when I run a mysql_num_rows test it is returning 0 rows. If you have any ideas thank you I appreciate it.
Are you sure that the column is called index? That is not an ideal choice for a column name because it is a reserved word. Normally the auto-increment column should be called id or similar.
If you really have called your column index then you need to quote it using backticks in your SQL queries:
SELECT * FROM chanels
WHERE videolocation != ''
ORDER BY `index` DESC
Edit yoru code like this
$query = mysqli_query("SELECT * FROM chanels
WHERE videolocation != ''
ORDER BY 'index' desc");
may it helps you
I am using the below code to try and echo out the latest 5 entries on the MySQL table, I cannot, however seem able to figure how to limit the number of results, can anyone help me out by allowing me to limit the number of results to 5 rows?
<table>
<?php
require_once($_SERVER['DOCUMENT_ROOT'] . "/resources/pdo.php");
$q = "SELECT * FROM `content` ORDER BY `id`";
$query = $pdo->query($q);
$data = array_reverse($query->fetchAll());
foreach ($data as $row) {
echo "<tr><td>{$row['title']}</td><td>{$row['id']}</td></tr>";
}
?>
</table>
Thanks!
Please note that I am new to PHP and I need help so if this question isn't useful, help me because I have only just started this.
Use LIMIT clause in your SQL query:
SELECT * FROM `content` ORDER BY `id` DESC LIMIT 5
From the manual:
The LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants (except when using prepared statements).
With two arguments, the first argument specifies the offset of the first row to return, and the second specifies the maximum number of rows to return. The offset of the initial row is 0 (not 1):
Use the LIMIT word:
SELECT * FROM `content` ORDER BY `id` DESC LIMIT 5
order by id desc to get rid of the array_reverse and limit 5 to cap the number of returned results.
$q = "SELECT * FROM `content` ORDER BY `id` DESC LIMIT 5";
...
$data = $query->fetchAll();
As a global guideline: when writing queries try to formulate them in such a way that the resultset is as close to what you need as possible, ie no extra sorting or filtering operations afterwards.
having the dbserver send data that you aren't going to use is a waste
having to resort/refilter data on the webserver costs webserver performance and, in the case of big resultsets, it can cost lots of memory as well
When pulling data from a database you normally set a LIMIT via the MySQL-query, instead of counting the loop-iterations when reading the returned data.
$q = "SELECT * FROM `content` ORDER BY `id` LIMIT 5";