I need to do pagination for table contain the following:
id.
name.
type (this contains: bad, good, great).
I need to order the result depending on type, first to appear 'great' then 'good' and last 'bad'. For example: I have 36 rows with type 'great', 25 with type 'good' and 13 with type 'bad' (total number of rows is 74), and I'm going to display 10 at each page. So at page 4 there will be 6 of type 'great' and 4 of type 'good'.
How to do such pagination?
On click of a button (arrow, , submit input, whatever suits you) send a parameter via get or post with the page number (starting with 0).
On your server side get the page number that you sent, check if it's valid and clean it off hazardous stuff (like injections of all sorts). Multiply it by some "pagesize" and then query the database for a range of records (order by type, id).
Example: 74 records, page 4, you pass page=3 as GET parameter and set it to some variable ($page), multiply it by page size and put into a query with offset and limit:
SELECT * FROM table
ORDER BY type DESC, id
LIMIT 10 OFFSET 30
where offset is calculated as $page * $pageSize, and limit is $pageSize. As a result you get 10 records from the range 31-40, sorted by type.
In this concrete example you can just alphabetically sort your types descending (since 'great' > 'good' > 'bad'), but you might need more advanced sorting for more different types.
Related
I'm trying to figure out the fastest way to get x rows from a table that are offset by x rows and ordered by a date column.
The problem I have is I'm paginating the rows from the query into pages of 10 rows per page, but I only need the nth page.
For example if I only need page 4 from the table, I need to select all the rows:
SELECT * FROM posts ORDER BY date
Then I need to paginate the array using PHP and get the 4th page (if it exists). This is less than ideal as it seems a waste to have to get the whole table.
Is there a better way to query the table in this situation?. For example if I have 10 posts per page and I want the the 4th page, is there a way to offset the query so it starts from the 30th row? (and ordered by date).
You're looking for LIMIT
SELECT * FROM posts ORDER BY date LIMIT 10, 20
Where 10 is offset and 20 is the number of rows
LIMIT is the answer. According to MySQL documentation,
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):
SELECT * FROM tbl LIMIT 5,10; # Retrieve rows 6-15
I'm working on an application that uses a scroll load system of 20 or so results loading into a feed at a time as you scroll. This feed consists of constantly added user generated content. Which means the result set can change per query that is offset by X.
So let's say we load 20 results, then scroll, another 20, and then before scrolling more to load the next 20, another user has uploaded a new piece of content, which effectively would present a duplicate in the next set of 20 results for the feed because we're using OFFSET to get additional results, and the total result set is getting shifted by 1 with this addition of new content that falls into the conditions of the query.
What is the best and most efficient way around this? We've dabbled with using the id of a row in a where condition to prevent duplicate results, and only using limit without offset for new results fetched.. so we could do WHERE id < 170 LIMIT 20, WHERE id < 150 LIMIT 20, WHERE id < 130 LIMIT 20, etc.. to control and prevent duplciates... HOWEVER, this does not work in every possible scenario as our result sets aren't always ordered with the id column ordered by DESC..
Soo.. what other options are there?..
Why are you using the where clause instead of limit with the offset option? Limit can take two arguments. The offset argument seems to do exactly what you want. For instance:
limit 100, 20
Takes 20 rows starting at the 101st row. Then:
limit 120, 20
Takes 20 rows starting at the 121st row. (The offsets start at 0 rather than 1 in MySQL counting.)
The one enhancement that you need to make is to ensure that the sort order for the records is stable. A stable sort is, essentially, one where there are no sort keys with the same value. To make this happen, just make the id column the last column in the sort. It is unique, so if there are any duplicate sort keys, then the addition of the id makes the sort stable.
You might want to try a database solution. On the initial request, create and populate a table. Use that table for the feed.
Make sure the tablename starts with something consistent, like TableToFeedMyApp, and ends with something guaranteed to make it unique. Then set up a scheduled job to find and drop all these tables that were created earlier than whatever you deem to be a certain interval.
So, I have a custom field type called "postorder." I added some php to the template page (see below) to call in the "postorder" for each of the posts, and to sort them in descending order. The problem I am having is that Wordpress is putting 10 after 1. So, the order of my posts is 1,10,2,3,4,5,6,7,8,9. I would like for 10 to come after 9, or find a different value to order my posts.
query_posts('showposts=1000&meta_key=postorder&orderby=meta_value&ASC&post_type='.portfolio);
WordPress is treating the values as string to sort, so 10 comes after 1, just change following
orderby=meta_value
to (values will be treated as number)
orderby=meta_value_num
When sorting by number, use meta_value_num instead of meta_value to make WordPress treat the value as a number instead of a string.
Does anyone know of a good resource on how to create the hyperlink numbers at the bottom of a results page as search engines do to load the next number of results?
The page would load the first 10 results. And then if you click on the number, it loads corresponding results in that 10 number range.
Example:
0-10 -> show no numbers
11-20 -> show 1, 2
21-30 -> 1, 2, 3
up to 50
anything more than 50 does 1,2,3,4,5.....67 [last number].
My thoughts so far (I'm doing this in PHP/mysqli but the logic is more important than the code):
$total = mysqli_num_rows($result) //total number of reqults from sql query
if ($total>10) {
$last = intval($total/10) + 1 //get the last number of the results
if($last <= 5){
for ($i, $i<$last, $i++){
//print the numbers as hyperlinks
} else {
//print 1 through 5 ... then $last
}
}
This though is static from only 1-5...last number while the search engines have it so if you click on the number, it remembers that number and bases the new logic on it. So if I click on the 5 in my formula, it should change to something like:
[previous] 3,4,5,6,7....67 [next]
And then I would just pass the number to the page itself again and limit the results based on what number was passed. Any suggestions also on the best way to pass the info?
You are looking for a pagination script. Visit this link The page is in Arabic but forth post is of pagination and you can download source for english or arabic version of pagination
Basically, you need two values to create a pagination, a limit and a offset.
1.The limit is the amount of items your are displaying at the same time.
2.The offset is from where you started your query.
So, let's say you have 5 items in each page and 25 items total.
In your query, you have to limit 5,0 (the amount of items and the position the query will start).
Now, if you divide 5(limit)/25(total) and you'll get 5 (amount of pages).
Now in page 0 (the start) you can get the offset by multiplying the page number with the limit, so 0 (page) * 5 (limit) gives you 0 (in the first page you start from the offset 0).
Now in the 3rd page, you multiply 3(page) * 5 (limit) it gives you 15, which means in page 3 (or four if you take into account that you actually started at page 0) you will display from offset 16 to 20.
Finally in page 4 (which to your users will be page 5 because they started at page 1, not page 0) you will display from offset 21 to 25 which are all the items in your query.
I am trying to implement the pagination in php. I am using the Mysql as back end database. I am trying to implement the pagination logic.
I would be having lots of record. But the user will see only 10 at a time.
Now to show the first page, i do a
SELECT * from USERS LIMIT 10.
Now to get the next 10 and the subsequent 10 records i am not able to write a query. Please help me fetch the in between records to support pagination logic. Also provide if any other suggestions for pagination.
You should use the OFFSET option.
SELECT * FROM Users LIMIT 10 OFFSET 10 (or 20, or 30);
That way you just pass the start position in the request when you hit next (or the page number) and you'll retrieve the records you want.
MySQL's limit feature can take two arguments:
select * from USERS limit 10,10
The above would retrieve 10 rows starting at row 10. Bear in mind that the MySQL row offset is 0 based, not 1. The first argument is the starting row, the second is the page size.
Also, if your page size is consistent, all you need to do is pass in the current page (default to zero). That would then allow you to specify the start row as a page * size.