Im making a query to the database where on the first query I limit the results to 4 by doing :
$result = mysql_query("SELECT * FROM members limit 4");
This gets me my first 4 entries in the DB and On my next query I want to get the next four what kind of approach should I take?
$result = mysql_query("SELECT * FROM members limit 4 count= 5");
LIMIT can take two arguments:
LIMIT {[offset,] row_count | row_count OFFSET offset}]
In your case you would do:
SELECT * FROM members limit 4,4;
But to do this consistently, you really should use some sort of ORDER BY, otherwise you are not assured to get consistent results.
sqlfiddle demo
You're close:
$result = mysql_query("SELECT * FROM members limit 3,4");
This tells MySQL to start returning rows at the fourth row (remember, mysql starts counting at zero so 0 is the first row and 3 is the fourth row) and return four rows total.
SELECT * FROM your_table LIMIT 3, 4;
Related
Say I have 50 rows in my database table and I wanted to start retrieving database entries starting with row 9.
How can I retrieve data from a database table starting at row 9?
My code for pulling data from my db table:
$sql = mysql_query("SELECT * FROM listheadlines ORDER BY id DESC LIMIT 20");
You can use OFFSET keyword like this:
$sql = mysql_query("SELECT * FROM listheadlines ORDER BY id DESC LIMIT 20 OFFSET 9");
To retrieve all rows from a certain offset up to the end of the result set, you can use some large number for the second parameter ( mysql.com ).
"SELECT * FROM listheadlines ORDER BY id DESC LIMIT 9, 18446744073709551615"
Or to get only 20 rows starting at offset 9:
"SELECT * FROM listheadlines ORDER BY id DESC LIMIT 9, 20"
Try this
mysql_query("SELECT * FROM listheadlines ORDER BY id Desc").setFirstResult(9);
Please check this once
How to fetch rows from middle of the table in mysql using hibernate?
I have 50+ rows and each have an id, how do i get the last 20 records and display each ones information with php.
Is the best way to use a loop? I want it to display the results quick and not miss any rows, is a loop the best way to go then?
This is the code that I have
$result = $mysqli_log->query("SELECT * FROM `$usern`");
while( $row = $result->fetch_array() ) {
$credit = $row['credit'];
echo $credit;
}
The MySQL query being executed doesn't specify any "order" to the rows; MySQL is free to return the rows in any order it chooses, so it's possible that the "last 20" rows on one run of the query might differ from the "last 20" rows on a second run.
(We do observe repeated behavior when the statement is re-executed; it usually takes some DML operations, the addition of an index, or an OPTIMIZE table statement, to actually get a change in the results returned... but the point is, there is no "last 20" rows in the table. In MySQL, it's just a set of rows.)
To specify a specific sequence of the rows, add an ORDER BY clause to the query. Assuming that you want to use the unique id column to order the rows, and you want the last 20 rows, and you want them returned in ascending id sequence:
SELECT t.*
FROM ( SELECT u.*
FROM `$usern` u
ORDER BY u.id DESC
LIMIT 20
) t
ORDER BY t.id
And, yes, processing rows "in a loop" in PHP, just like you demonstrate, is a normative pattern.
To limit the number of queries use Limit and order them desc by your ID
Select *
From `$usern`
Order By ID Desc
Limit 20
To Flip them back in the forward order you can use a derived table
Select *
From (Select ID, Test
From test
Order By ID Desc
Limit 3) d
Order By ID Asc
If you need the newest 20 records, you have to ORDER DESC the result set by ID and then LIMIT that set result to 20 records.
So you can
use something like this:
$result = $mysqli_log->query("SELECT * FROM `$usern` ORDER BY `ID` DESC LIMIT 20");
while( $row = $result->fetch_array() ) {
$credit = $row['credit'];
echo $credit;
}
Another good approach, if you are using associative keys like $row['credit'], is to use featch_assoc instead of featch_array (if your framework provides such a function)
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 have a mysql table. It has auto increment on the id. but I regularly delete rows so the numbers are all over the place. I need to get the last n rows out, but because of deletions, the common way of using the max of the autoincremented id column doesn't work well...
1 - Is their another way to get the bottom 50?
2 - Is their a way to get rows by actual row number? so if I have 4 rows labelled 1,2,3,4 delete row 2 then it will become 1,2,3 rather than 1,3,4?
SELECT ... ORDER BY id DESC LIMIT 50
SELECT *
FROM TABLE
ORDER BY id DESC
LIMIT 50
EDIT
To pick the last 50, but sort by id ASC
SELECT X.*
FROM ( SELECT *
FROM TABLE
ORDER BY id DESC
LIMIT 50
) X
ORDER BY X.id
1 - First get total row count like
SELECT COUNT(*) AS c FROM ...
then use
SELECT ..... LIMIT [start],[count]
2 - One idea is to use view , or procedure, but this is much more harder and may be used when there is no other way to avoid this
1 - Is their another way to get the bottom 50?
SELECT * FROM table_name ORDER BY record_id DESC LIMIT 50
2 - Is their a way to get rows by actual row number? so if I have 4 rows labelled 1,2,3,4 delete row 2 then it will become 1,2,3 rather than 1,3,4?
SELECT * FROM table_name
1 - Yes but it is ugly afaik, you do a
SELECT whateveryouwant FROM table ORDER BY yourprimarykey DESC LIMIT 50
the you fetch the rows into an array and reverse the array, in php :
$r = mysql_query('SELECT * FROM table ORDER BY primarykey DESC LIMIT 50');
$set = array();
while($row = mysql_fetch_assoc($r)) $set = $row;
$set = array_reverse($set);
foreach($set as $row) {
// display row ...
}
2 - You'll have to manage your primary key by yourself, its a bit risky ...