How Can I Skip every other row in mysql? - php

Question

i have a table in mysql and i am fetching the results from this table. but instead of fetching all the rows in this table i only want to fetch every other row. so first get row one then skip the second row, get row 3 and skip row 4 etc.
Is there a way of doing this and if so can someone please show me how.
I've tried this:
function:
function blocked_users_list() {
global $connection;
global $_SESSION;
global $profile_id;
$query = "SELECT
baseview.*
#odd:=1-#odd AS even
FROM
(
SELECT *
FROM ptb_block_user
WHERE
WHERE ptb_block_user.blocked = '1'
AND ptb_block_user.blocked_id = ".$_SESSION['user_id']."
) AS baseview,
(
SELECT #odd:=0
) AS filter
WHERE
even=1
";
$blocked_users_list = mysql_query($query, $connection);
confirm_query($query, $connection);
return $blocked_users_list;
}
php:
<?php
$blocked_users_list = blocked_users_list();
while ($block = mysql_fetch_array($blocked_users_list)) {
?>
but it gives this error:
Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in /Applications/XAMPP/xamppfiles/htdocs/ptb1/blocked_users.php on line 44

Answer 1

do it in the query:
SELECT *
FROM (
SELECT
#row := #row +1 AS rownum, [column name]
FROM (
SELECT #row :=0) r, [table name]
) ranked
WHERE rownum % [n] = 1

Answer 2

You can use modulus in mysql (one query)
select * from `table` where `id` % 2 = 1
Retrieves all odd IDs.

Answer 3

Assuming you have a query like
SELECT
col1 AS colA,
col2 AS colB
FROM
sometable
WHERE
something=17
that fetches all rows as a baseline. You can then filter every second row by using
SELECT
baseview.*
#odd:=1-#odd AS even
FROM
(
SELECT
col1 AS colA,
col2 AS colB
FROM
sometable
WHERE
something=17
) AS baseview,
(
SELECT #odd:=0
) AS filter
WHERE
even=1

Answer 4

Use a variable to record the index, then check with mod 2 ($ind % 2) - this will return either 0 or 1.
<?php
$users_list = users_list();
$ind = 0;
while ($user = mysql_fetch_array($users_list)) {
if(($ind++)%2) echo "something";
}
?>