I am making a site which allows admins to basically add points for a user.
At this point in time, I have a table, where id_child is unique, and id_points changes. So a constant stream of id_points can come in, however, it will only show the latest id_points, not the total.
I am wondering how I could go about creating a PHP script that could add all of those together.
From the image, the idea is that I want all id_points values added together to give a total, and this is for the same id_child
Use SQL sum() funciton:
select sum(id_points) from table `table_name` where `id_child` = 1
Hope i understood right.
First if you want to show only the latest points added you have to create another table #__points where you will keep every new change of points.
You need 3 columns id as PRIMARY and AUTO_INCRENMENT , pts and user_id . user_id will be FK to id_child.
So when you want to add a new record :
INSERT INTO `#__points` (pts,user_id) VALUES ("$pts",$id)
When you want to select last inserted value for each admin :
SELECT * from `#__points` where user_id=$id ORDER BY id ASC LIMIT 1
Related
I have a table with data relating to a user, and two important columns:
refer_count, which is updated when a new entry is made in the table with the referred_by column set to that users user_id, and referred_by which is the user_id of the of the user that referred them.
I want to select the users from the table that have the highest number of referrals after a certain date.
For example:
If there are 3 users, one of which referred the other 2 (lets say users 2 and 3), however user 2 was referred on the 2/12/14, whereas user 3 was referred on the 3/1/15.
If the cutoff is 1/12/14, then user 1 is returned with refer_count set to 2, but if the cutoff is after 2/12/14, then user 1 is returned with refer_count set to 1.
I've been thinking of how to do this, but I can't think of a way that would work. Is there a way?
This is via MySQL.
EDIT: I think I may need to provide for information.
The date registered (register_date) is used as the refer date. I need the refer_count to be updated with the number of users referred after the cutoff, however I need to get the actual user. This is for a 'top referrers' table. I can't figure out why I'm having so much trouble thinking of a way to do this.
SELECT user_id FROM usertable WHERE (referal_date BETWEEN '2014-12-2' AND CURDATE())ORDER BY refer_count DESC;
That's the rough idea.
You should look into normalizing your tables if you're keeping that all in the same table, though. It'd be better to keep referals in a seperate table.
Get the row with the maximum in refer_count with a Date condition for your referal_date such that it's after the certainDate:
SELECT user_id FROM table WHERE refer_count = (SELECT MAX(refer_count) FROM table) AND referal_date>certainDate;
Note that WHERE is before SELECT so it will not get the highest count first, but will filter with the date condition then get the highest count.
Edit: Updated query based on edited question.
I'm thinking of implement a view history for my wordpress blog, where users can view their previously viewed articles as a list in their account page.
I would like to limit this to 24 unique page history per user at any point of time, meaning, if the number of articles exceeds 24, the oldest article row would be deleted, and the new article added to the table.
I'm using PHP and MySQL.
Here's my current thoughts on implementation:
Create a table with user_id and post_id columns
When user views an article, insert new row into the table
Select the rows with the current user_id, and if number of rows is more than 24,
Delete the oldest row
I'm not sure if this is the best method, since it's 3 additional database queries per user page view which is pretty heavy.
Is there a better way to do this?
The ideea is good. Improve it by updating the oldest row instead of deleting it and then adding a new one. ;)
Also make a single read query and a single write query.
make a query that is like this one
SELECT (SELECT COUNT(*) FROM recentArticles WHERE userID = 23)
AS NoOfArticles, articleID, timestamp
FROM recentArticles
WHERE userID = 23
ORDER BY timestamp ASC
LIMIT 1;
If NoOfArticles < 24 then execute an insert query, else execute an update query to articleID
You could always implement this using cookies to key on which pages have been visited and keeping a running list on the users PC. This will reduce the traffic to the site, put the processing scripts on the user-side, and could be easier to implement.
That being said, I agree with the other answer about updating the oldest entry if the table is full. This eliminates the need to delete and add a row. Key off a time-date stamp to sort the entries when you're displaying them and to figure out which page was the oldest (and needs to be updated if >= 24 pages.
You can merge two queries in one. In this way, You will save execution time of your script. So, basically, DELETE row if the post count is more than 24. You can modify this query according to your exact need. But yes, you can think on this way.
DELETE FROM `table_name`
WHERE id=(SELECT (CASE WHEN COUNT(id)>24 then id END)
AS last_id
FROM `table_name`
WHERE user_id='XX'
ORDER BY id DESC LIMIT 1);
I would like to know how to update my database table with new data but having the latest data be at the top with the unique id starting at 1. Here's what I mean:
First insert query, for example, inserts 3 article topics:
id article
1 firstNews
2 secondNews
3 thirdNews
Then the next time I run a Cron job to check for new articles, for example two new articles appear, I want the two new articles to be in the beginning of the table, like this:
id article
1 NewArticle1
2 NewArticle2
3 firstNews
4 secondNews
5 thirdNews
Hope that made sense. This might be a bad way to do it, I guess I could have a column with insert date() and then get the data out OrderBy date but it has to be an easier way to do this. I think this would be the easiest to output the most recent data from the table...
If I do ORDER BY DESC, it would output NewArticle2 before NewArticle1, which would defeat the purpose...
id article
1 firstNews
2 secondNews
3 thirdNews
4 NewArticle1
5 NewArticle2
So by DESC, id 5 would be the first one output...I was really hoping there was a way around this...
You should never do this. Just insert at the end, and to get the latest articles, use a query:
SELECT * FROM articles ORDER BY id DESC;
In general: Don't fit the data to your query, fit the query to your data. The id is not a position or number, it uniquely identifies that row of data.
You could use a Date columns and sort on that. Or just sort by ID descending.
It's rarely a good idea to change a PK in place. Not least, you mah have child tables using that PK and maybe history tables too
Note that there is no implicit order to a SQL table: you always need an ORDER BY to guarantee the resultset order
You should add another column specifically for sorting, e.g. a date. and add an INDEX on it.
Then the query becomes:
SELECT *
FROM news
ORDER BY newsdate DESC
Latest news comes first
If there are two news items that could be posted at exactly the same time, you may wish to include a secondary sort:
ORDER BY newsdate DESC, id ASC
It shouldn't be your concern at all.
ID is not a number nor a position by any means. It's just an unique identifier.
Means every database row sticks to it's id forever. While you want to assign your "unique" id to the every newcoming news, which makes no sense.
So, just have usual autoincremented id and select it using ORDER BY id DESC to have latest entries first.
I have a web application that stores points in a table, and total points in the user table as below:
User Table
user_id | total_points
Points Table
id | date | user_id | points
Every time a user earns a point, the following steps occur:
1. Enter points value to points table
2. Calculate SUM of the points for that user
3. Update the user table with the new SUM of points (total_points)
The values in the user table might get out of sync with the sum in the points table, and I want to be able to recalculate the SUM of all points for every user once in a while (eg. once a month). I could write a PHP script that could loop through each user in the user table and find the sum for that user and update the total_points, but that would be a lot of SQL queries.
Is there a better(efficient) way of doing what I am trying to do?
Thanks...
A more efficient way to do this would be the following:
User Table
user_id
Points Table
id | date | user_id | points
Total Points View
user_id | total_points
A view is effectively a select statement disguised as a table. The select statement would be: SELECT "user_id", SUM("points") AS "total_points" FROM "Points Table" GROUP BY "user_id". To create a view, execute CREATE VIEW "Total Points View" AS <SELECT STATEMENT> where SELECT STATEMENT is the previous select statement.
Once the view has been created, you can treat it as you would any regular table.
P.S.: I don't know that the quotes are necessary unless your table names actually contain spaces, but it's been a while since I worked with MySQL, so I don't remember it's idiosyncrasies.
You have to user Triggers for this, to make the users total points in sync with the user_points table. Something like:
Create Trigger UpdateUserTotalPoints AFTER INSERT ON points
FOR EACH ROW Begin
UPDATE users u
INNER JOIN
(
SELECT user_id, SUM(points) totalPoints
FROM points
GROUP BY user_id
) p ON u.user_id = p.user_id
SET u.total_points = p.totalPoints;
END;
SQL Fiddle Demo
Note that: As noted by #FireLizzard, if these records in the second table, are frequently updated or delted, you have to have other AFTER UPDATE and AFTER DELETE triggers as well, to keep the two tables in sync. And in this case the solution that #FireLizzard will be better in this case.
If you want it once a month, you can’t deal with just MySQL. You have too « logic » code here, and put too logic in database is not the correct way to go. The trigger of Karan Punamiya could be nice, but it will update the user_table on every insert in points table, and it’s not what you seem to want.
For the fact you want to be able to remove points, just add bsarv new negated rows in points, don’t remove any row (it will break the history trace).
If you really want it periodically, you can run a cron script that does that, or even call your PHP script ;)
I have a voting script which pulls out the number of votes per user.
Everything is working, except I need to now display the number of votes per user in order of number of votes. Please see my database structure:
Entries:
UserID, FirstName, LastName, EmailAddress, TelephoneNumber, Image, Status
Voting:
item, vote, nvotes
The item field contains vt_img and then the UserID, so for example: vt_img4 and both vote & nvotes display the number of votes.
Any ideas how I can relate those together and display the users in order of the most voted at the top?
Thanks
You really need to change the structure of the voting table so that you can do a normal join. I would strongly suggest adding either a pure userID column, or at the very least not making it a concat of two other columns. Based on an ID you could then easily do something like this:
select
a.userID,
a.firstName,
b.votes
from
entries a
join voting b
on a.userID=b.userID
order by
b.votes desc
The other option is to consider (if it is a one to one relationship) simply merging the data into one table which would make it even easier again.
At the moment, this really is an XY problem, you are looking for a way to join two tables that aren't meant to be joined. While there are (horrible, ghastly, terrible) ways of doing it, I think the best solution is to do a little extra work and alter your database (we can certainly help with that so you don't lose any data) and then you will be able to both do what you want right now (easily) and all those other things you will want to do in the future (that you don't know about right now) will be oh so much easier.
Edit: It seems like this is a great opportunity to use a Trigger to insert the new row for you. A MySQL trigger is an action that the database will make when a certain predefined action takes place. In this case, you want to insert a new row into a table when you insert a row into your main table. The beauty is that you can use a reference to the data in the original table to do it:
CREATE TRIGGER Entries_Trigger AFTER insert ON Entries
FOR EACH ROW BEGIN
insert into Voting values(new.UserID,0,0);
END;
This will work in the following manner - When a row is inserted into your Entries table, the database will insert the row (creating the auto_increment ID and the like) then instantly call this trigger, which will then use that newly created UserID to insert into the second table (along with some zeroes for votes and nvotes).
Your database is badly designed. It should be:
Voting:
item, user_id, vote, nvotes
Placing the item id and the user id into the same column as a concatenated string with a delimiter is just asking for trouble. This isn't scalable at all. Look up the basics on Normalization.
You could try this:
SELECT *
FROM Entries e
JOIN Voting v ON (CONCAT('vt_img', e.UserID) = v.item)
ORDER BY nvotes DESC
but please notice that this query might be quite slow due to the fact that the join field for Entries table is built at query time.
You should consider changing your database structure so that Voting contains a UserID field in order to do a direct join.
I'm figuring the Entries table is where votes are cast (you're database schema doesn't make much sense to me, seems like you could work it a little better). If the votes are actually on the Votes table and that's connected to a user, then you should have UserID field in that table too. Either way the example will help.
Lets say you add UserID to the Votes table and this is where a user's votes are stored than this would be your query
SELECT Users.id, Votes.*,
SUM(Votes.nvotes) AS user_votes
FROM Users, Votes
WHERE Users.id = Votes.UserID
GROUP BY Votes.UserID
ORDER BY user_votes
USE ORDER BY in your query --
SELECT column_name(s)
FROM table_name
ORDER BY column_name(s) ASC|DESC