My code get the last 10 values from a table. This table has te structure id,text and by the moment it has 20 rows. I use this piece of code
<?php
$query = mysql_query("SELECT * FROM `table` ORDER BY `id` DESC LIMIT 10");
// Fetching data stuff here
?>
and it returns the data for IDs 11-20. (The last 10 of the 20)
I want to get the previous 10 values from this 1-10 via AJAX. I thought maybe this will work
$previous_id= $_GET["last"]; // This time it will be 11
mysql_query("SELECT * FROM `table` ORDER BY `id` DESC LIMIT $previous_id, -10");
But I'm doesn't, any suggestion?
Thanks
PS: This is not a gimme teh codez question, I just want to know how to make that query work.
If I understand you correctly you want to get the 10 rows before the row with id = $previous_id, ordered by descending ID.
If that's the case your best bet would be to use a WHERE condition. As you are ordering by id DESC you want the first 10 rows with id > $previous_id:
SELECT * FROM `table` WHERE `id` > $previous_id ORDER BY `id` DESC LIMIT 10
These will be the 10 rows before $previous_id in your original query.
Simply use positive number instead of -10:
"SELECT * FROM `table` ORDER BY `id` DESC LIMIT $previous_id, 10"
Let's suppose $previous_id is 5, the query would be:
"SELECT * FROM `table` ORDER BY `id` DESC LIMIT 5, 10"
The returned rows will be starting from 5 and 10 records.
Related
For a statistics table, I am pulling the data to be the last 5 records with DESC over SQL. But the data I shoot comes in the form of 6,5,4,3,2. When I take it as ASC, I get the first 5 records instead of the last 5 records. Take the last 5 records by sorting the data I want to make as 2,3,4,5,6
The function I use
$query = $db->query("SELECT * FROM `table` WHERE `username`='".$username."' ORDER BY id DESC LIMIT 5")
In summary ; The last data I pulled as ASC is listed upside down on the Chart, I want it to be sorted as 2,3,4,5,6
The result I got now
If you need to sort will be done in MySQL can use next:
SELECT tmp.* FROM (
SELECT *
FROM `table`
WHERE `username`='".$username."'
ORDER BY id DESC LIMIT 5
) tmp
ORDER BY tmp.id ASC;
If you're just pulling a small set, just use PHP built in functions like sort or any other function (https://www.php.net/manual/en/array.sorting.php)
If it is a large data set, i'd avoid try to do that directly on the query, something like this:
$db->bind('username',$username);
$query = $db->query('
SELECT * FROM (
SELECT * FROM `table` WHERE `username` = :username ORDER BY id DESC
) qry ORDER BY id'
);
I didnt test the query, but i would something similar to this.
I'm trying to keep the 10 most recent entries in my database and delete the older ones. I tried DELETE FROM people ORDER BY id DESC LIMIT $excess, but it just deleted the top 10 entries.
$query = "SELECT * FROM people";
$result = mysqli_query($conn, $query);
$count = mysqli_num_rows($result);
if ($count > 10) {
$excess = $count - 10;
$query = "DELETE FROM people WHERE id IN(SELECT id FROM people ORDER BY id DESC LIMIT '$excess')";
mysqli_query($conn, $query);
}
You can use this:-
DELETE FROM `people`
WHERE id NOT IN (
SELECT id
FROM (
SELECT id
FROM `people`
ORDER BY id DESC
LIMIT 10
)
);
Also your query is logically incorrect and you are fetching the records in descending order. i.e. Latest to older and you are deleting the most recent records. Use ASC instead.
Something like this? Gets the ten latest ids in the subquery, then deletes all of the other ids.
DELETE FROM people WHERE id NOT IN (SELECT id FROM PEOPLE ORDER BY id DESC LIMIT 10)
Your logic is all over the place, [you should ORDER BY ASC, not DESC] and your query will take ages if there are [for example] 10,000 entries because you'll have an IN clause with 9,990 entries to compare all 10,000 to.
Select the 10 most recent, and delete where NOT in.
DELETE FROM people
WHERE id NOT IN(
SELECT id
FROM people
ORDER BY id DESC
LIMIT 10
)
Maybe find the ID of the 10th element and then delete all rows which are older?
I have a table containing rows with timestamped.
Normally if I want to get the latest 20 rows out according to the time. I use:
$sql = "SELECT *
FROM comment
ORDER BY time DESC
LIMIT 20";
But now, I want to get the latest comments AFTER the latest 20 rows and LIMIT to 10. That means rows 21-30.(of course , everything is according to timestamp)
How can I do that using MySQL?
MySQL has a built-in offset that you can use with LIMIT:
$sql = "SELECT * FROM comment ORDER BY time DESC LIMIT 10, 20";
Also, refer to this SO post: MySQL LIMIT/OFFSET: get all records except the first X
$sql = "SELECT * FROM comment ORDER BY time DESC LIMIT 20, 10";
Hope it will select from 21 to 30 records
sql = "SELECT * FROM comment ORDER BY ID DESC LIMIT 20, 10";
Try a mixture of limits
$sql = "select * from (SELECT * FROM comment ORDER BY time DESC LIMIT 30) as A order by time ASC limit 10";
The mysql built in offset method others have posted looks better though.
There are two options:
Get 30 rows and use PHP to split the result set into a group of 20
and a group of 10.
Send two queries, one for 20 and one for 10 rows.
I want to return only the last 15 rows in my table, then the 15 before that.
Unfortunately while($rows = mysql_fetch_assoc($result)) where the query is SELECT * FROM table returns the data in all rows.
I thought about doing something like:
In my insert script
SELECT * FROM table then $selection_id = mysql_num_rows($result)-14 before inserting any data, then adding column named selection_id which would contain $selection_id, thus each set of 15 rows would have the same selection_id.
In my select script
SELECT * FROM table then $num_rows = mysql_num_rows($result)/15 then SELECT * FROM table WHERE selection_id='$num_rows' and SELECT * FROM table WHERE selection_id='$num_rows-1'.
I could then perform while(..) on both results as usual.
However, I'm not sure this is the most efficient way (chances are it's not), so if not, I'd really appreciate some suggestions to cut down the amount of code I'll have to use :)!!
Use a LIMIT clause in your query, order by your auto-incrementing primary key in descending order. E.g.
SELECT * FROM `table` ORDER BY `selection_id` DESC LIMIT 0,15
...will get the last 15 rows, and:
SELECT * FROM `table` ORDER BY `selection_id` DESC LIMIT 15,15
...will get the 15 rows before that.
Selecting the last 15 rows:
SELECT *
FROM `table`
ORDER BY `id` DESC
LIMIT 0,15
Selecting the 15 rows before the previous ones:
SELECT *
FROM `table`
ORDER BY `id` DESC
LIMIT 15,15
And you can continue in a while cycle.
You need to check out mysql LIMIT. To get the last 15, you'd need to know the number of total rows.
$offset=$rowcount-15;
$sql="SELECT * FROM mytable LIMIT $offset,15";
This is just for example, you'd want to make sure there are at least 15 rows, I'm not sure how mysql would deal with a negative offset. I'll let you figure out how to count the rows.
Edit:
Oh, haha, you could also just sort it descending, that will save you having to query twice.
SELECT * FROM mytable ORDER BY id DESC LIMIT 15;
I need help on how to randomize the last 10 rows of MySql records.
$mysqld = mysql_query(select * from table where amount > amount2 and code = '$code' order by time DESC limit 1);
From the statement above I need to randomize the last 10 rows ordered by time but limited only 1 to display.
EDIT: In other words, I need to have the table ordered by time and then I need to focus on the last 10 rows. From these last 10 rows, I need to pick one and it must be random, which one I get.
Is this possible?
Thanks
Assuming that time is the time when record was inserted, this will get you the latest 10 rows from the table:
SELECT * FROM `table` WHERE `amount` > `amount2` AND `code` = '$code'
ORDER BY `time` DESC LIMIT 10
Now, you can use the result as a temporary table, sort it randomly (as it's only 10 rows) and return one row:
SELECT * FROM (
SELECT * FROM `table` WHERE `amount` > `amount2` AND `code` = '$code'
ORDER BY `time` DESC LIMIT 10
) AS temptable
ORDER BY RAND()
LIMIT 1
Try....
SELECT * FROM (SELECT * FROM yerTable ORDER BY id DESC LIMIT 10) AS tmp ORDER BY RAND() LIMIT 1
Obviously replace id with any other distinct column if preferred.