Is there a way to add articles (data) in mysql/php but make them
auto-publish during the day when I´m not available.
So lets say, if I have a news site but I´ll be busy tomorrow the whole day so I could pre-write articles the day before with timestamp and they would appear when I want
Is this possible?
How would the script be like:
SELECT FROM articles WHEN TIME is 2011-12-01 12:15
Thanks
As simple as:
SELECT * FROM articles WHERE timestamp <= NOW()
Though I never worked with them to me the easiest solutions seems to be Cronjobs combined with an extra waiting table and a script linking both.
You pre-write your article and store them in table together with the time stamp you want to publish them.
Your cron will invoke a script every 2,3, 5 hours (twice a day, whatever).
This script checks the time stamps in the table against the actual time and if it is about time to realise the article it will do so (or hand the information to the realise script).
Related
How should I store Birthdate's in MySQL so that I can easily update everyone's Age on a daily basis via a Cron Job?
Does it even make sense to store the Age AND the Birthdate so that when searches involving the Age are made, I don't have to calculate each Age on-the-fly and waste CPU resources?
If so, how should I 1) store the Birthdate, and 2) calculate the Age each day?
I can imagine the daily cron script first filtering out the user's whose Birthdate month is not the current month, then filtering out the user's whose Birthdate day is not the current day, and then incrementing by one the age of each user that is left.
Does this make sense? If so, how would I do that? Is there a better way to do all of this?
The simple answer is don't; never store a persons age. It changes for each person yearly but, as you say, you have to check that it's correct for every person daily.
Only store the date of birth, and then calculate the age when selecting from the database. It's only today - date of birth so takes almost no CPUs at all.
EDIT:
To expand upon my comment in ManseUK's answer there's also the possibility of failure. What happens if your server / database is down? Or your update fails to run at its specified time? Or someone comes along and runs it manually after the update already been run for that date? Or someone turns off your scheduler? There's no danger of this happening if you calculate Age as you select from the database.
To select where age is between 25 and 30 years and assuming a DATE column dateofbirth your query would be something like:
select *
from users
where dateofbirth between date_add( curdate(), interval -30 year )
and date_add( curdate(), interval -25 year )
Ensure users is indexed on dateofbirth.
No, don't store age, just calculate it in your queries. As for the birthday, I prefer to have all my date/time in unix timestamps (because I hate to deal with portability across date-format-changing locale settings)
Does it even make sense to store the Age
No.
I don't have to calculate each Age on-the-fly and waste CPU resources?
As a matter of fact, you'd waste a zillion more "CPU resources" (of which you have too vague idea to be concerned of) with your everyday update approach.
Is there a better way to do all of this?
Store the birthdate and calculate the age at select time
what if you want to find out all the ones whose Age is greater than 25 but less than 30?
this is quite trivial query like this
WHERE birth_date BETWEEN date_sub(curdate(), INTERVAL 25 YEAR)
AND date_sub(curdate(), INTERVAL 30 YEAR)
the query would using an index (if any) and thus be blazing fast, without any [unnecessary] denormalizations
Im going to go against the majority all of the answers here.
I would store both ...
updating the age is quick and simple - a single mysql query could run every day and its done
calculating the age is time consuming when you have lots of page views - amount of times its viewed far outweighs the number of changes
Just imagine a table scenario - a table with 100 or 1000 rows that shows the age of a person ... how long is that going to take to compute ???
I always thought that Stackoverflow calculated the Reputation dynamically but you can see on the Stackoverflow data explorer that they dont - see the User object in the schema on the right. Its recorded and updated each time its changed - I would guess that this is purely because of the amount of times its viewed far outweighs the number of changes
I don't think it's totally true that computing age dynamically takes a lot of memory.
Why not create a table CALENDAR with 365 rows 1 row for each day of an year. And store a list of userid against the day corresponding to their birthday.
For each day just refer the table entry for that day and refresh the age of only those selected users.
This will reduce the complexity greatly even when the user base increases.
I am creating a system that requires a schedular for a particular task. Users may pick from times 24 hours a day, 7 days a week.
I came up with a few options for the database storage, but I don't think either one is the most efficient design, so I'm hoping for some possible alternatives that may be more efficient.
On the user side I created a grid of buttons with 2 loops to create the days, and the times, and I set each a unique value of $timeValue = "d".$j."-t".$i;
So d1-t0 will be Saturday at Midnight d3-t12= Tuesday at Noon, and so forth.
So, in the database I was first going to simply have a ID, day, time set up, but that would result in a possible 168 rows per event
Then I tried an ID, day, and time 0-23 (a column for each hour of the day) And I was simply going to have a boolean set up. 0 if not selected, 1 if it is.
This would result in 7 rows per event, but I think querying that data might be a pain.
I need to perform a few functions on this data. On each day, list the number of selected times into an array. But I don't believe having a select statement of SELECT * from schedule where time0, =1 or time1= 1 .... ect will work, nor will it produce the desired array. (times=(0,3,5,6,7...)
So, this isnt going to work well.
My overall system will need to also know every event that has each time selected for a mass posting.
"Select * from table where time = $time (0-23) and day= $day (1-7)
Do action with data...
So with this requirement, I'm going to assume that storing the times as an array within the database is likely not the most efficient way either.
So am I stuck with needing up to 168 rows of data per event, or is there a better way I am missing? Thanks
Update:
To give a little more clarity on what I need to accomplish:
Users will be creating event campaigns in which other users can bid on various time slots for something to happen. There will likely be 10-100 thousand of these campaigns at any one time and they are ongoing until the creator stops them. The campaign creators can define the time slots available for their campaign.
At the designated time each day the system will find every campaign that has an event scheduled and perform the event.
So the first requirement is to know which time slots are available for the campaign, and then I need the system to quickly identify campaigns that have an event on each hour and day and perform it automatically.
I am trying to set up a database to record the last 30 days of information for each user. The data will be recorded once a day (i.e. by a cron job) and will be the value of an item (i.e. constantly changes).
What would be the best way to structure this? I was thinking of setting a table and then just storing the 30 days in the table and deleting the 31st day as I add the new day with the cron job (and shifting all of the others up one day) but this doesn't seem very efficient..
Thanks for the help.
What you can do is store the current date with each entry, then in your cron job, delete all entries that are greater than thirty days old.
For example (with MySQL),
DELETE FROM user_statistics WHERE DATEDIFF(NOW(), date_of_record) > 30;
Store the user data with its own date and delete the oldest when you exceed your limit. No need to shift anything.
I'd log by actual date using a DATE column. You can query up "last 30 days" pretty easily in MySQL.
As for purging, the cron job can delete anything older than 30 days pretty easily as well. Or, since it's so easy to ignore anything older than 30 days, you might even choose to not delete older records (at least not every day).
I'm trying to create a computer reservation system, where user chooses a computer and select the time how long he will be using this PC. In that time other persons can't reserve this pc, I need to find a solution, how to automaticaly delete all rows containing reserved pc's after their time expires. Thank you for the advice.
The common way to handle this is to store an expires_at timestamp on the reservation row. Then your query to find any "open" reservations would have WHERE 'expires_at' < NOW() or something similar.
This is an untested answer, that may only be a suggestion, but I just started looking at these, so am interested in feedback as well. i'm still working through possibilities and drawbacks, but it might well suit your need.
Take a look at MySQL Events, an article about it is here, and official syntax at Mysql Docs.
Per the article:
An event is similar to a trigger. However, rather than running in
response to a data change, events can be scheduled to run any number
of times during a specific period. In effect, it’s a database-only
cron job.
Pondering this, I'd envision a procedure that deleted anything >1hr (if that's the expiration). This procedure would be TRIGGERED on new inserts to get rid of anything expired at that moment, but also in an event to run every 15 minutes or so so that automatic deletes by the trigger aren't dependant on somebody else adding a reservation to trigger that procedure.
If your server is linux, you can use cron jobs to check once a day every reservation dates. If these dates have expired .. modified field reserves to be available.
Normally I would do it this way:
when storing a reservation, store date_from and date_to both of datatype DATETIME
when checking if there is a computer free check for all computers and filter with WHERE '{$my_date}' >= date_to AND '{$my_date}' <= date_from - by this You should be able to get all the PCs that are not reserved within a certain time...
To be complete in the solution, you need to run a CRON job which calls a query to remove all reservations that have a reservation_time + (15 * 60) < unix_timestamp().
I am assuming you have a time that the reservation was placed or started and are using UNIX/Epoch Timestamps.
Instead of doing a expires_now, if you know it will always be a fixed interval ie 15 minutes, you can do:
DELETE FROM reservations WHERE reservation_time + (15 * 60) < unix_timestamp()
Something you could look into is managing cron job's from PHP, http://www.highonphp.com/cron-job-manager.
The above script will, when a reservation is created, insert an entry into /etc/cron.d/ and you could configure it to run at the expected reservation endtime. Then inside the php file which would be executed, you could do:
DELETE FROM reservations WHERE id = :id
I am developing a website which will have 200.000 pages. There is also a browse section, which shows most popular, highest rated etc. documents. However this section will become almost static couple of weeks later, after launch. So I also would like to implement a filtering system which will show today's, this week's, this month's most popular items, just like youtube.
Just like this:
http://www.youtube.com/videos?c=2
How should I implement this function? Do I need another table, which will have a new entry for every document each day?
docid, date, view_count, rating
So I will get today's row for filtering by using a day, or calculate a week (7 rows) for filtering by using week? It seems not efficient. Do you have any suggestions?
I am using LAMP stack by the way.
Thanks,
Assuming you timestamp the records in your table, you should be able to put a where clause that limits the timestamp to whatever timeframe you want.
You can cache the result, especially the longer ones, for long enough to make the request inconsequential.
EDIT
But perhaps you mean most popular today, not most popular that was added today?
In which case, I don't have an answer.
The most direct approach is to save the timestamp and the resource id each time the resource is shown in recent_views(what, when). Daily/weekly/monthly charts can be created with appropriate WHERE clauses like WHERE when > $beginOfPeriod AND when < $endOfPeriod.
For performance reasons you can aggregate the values each night, save the sums in separate tables like daily_views(what, sum) and truncate the source table.
I guess I would calculate the date's in code and then pass them as arguments, to the SQL you are using.
I would do it using a compiler. Youtube probably does that too, considering the amount of traffic and the response times.
The principle is easy to understand. You log every every view or rating in a page_view table. You define periods at which the compilation occurs (hourly, daily, weekly, monthly). Every time you hit the good time (e.g.: end of the day), you execute the compiler, which essentially execute a query à-la...
SELECT * FROM page_view WHERE date > $from_date AND date < $to_date
... and store the result. This probably works better in a cron job.
The next time you need to display the information, you can just fetch the stored result and display it without re-computation. There are a variety of storage methods you can use: a MySQL table (e.g.: page_view_compiled), memcached, etc.