Hope I can explain the problem I'm having trouble with.
I have to write a stepwise methodology using pseudocode/SQL query to auto generate a list of products/items with low stock/expiry from the inventory database.The list must be updated at 12 a.m. daily.
I tried this
CREATE EVENT IF NOT EXISTS update_table
ON SCHEDULE EVERY 1 DAY STARTS '2022-05-22 00:00:00'
ON COMPLETION PRESERVE ENABLE
Do
Select inventory.products from inventory where inventory.stocks <
inventory.required_stocks.
Your stated requirement is to run some sort of report very soon after the beginning of each calendar day.
The next question you must answer is this: What will you do with that report? Will you simply drop it into "low_stock" table someplace in your database? Will you format it into an email message and send it to your purchasing department? It will be difficult to make "pseudocode" for your requirement without first analyzing the overall business process you intend to enhance.
Various RDBMS systems have ways of doing scheduled things at particular times of day. You've shown the EVENT setup provided by MariaDB / MySQL. SQL Server has their "Jobs" system. postgreSQL has the pg_cron extension. Yo
The thing is, you can't just do SELECT operations from within these scheduled database actions: the result sets have noplace to go from that context. You can do CREATE TABLE midnight_run AS SELECT whatever ... to place the results in a table. But then the results are in another table.
If you want to get the results out of the DBMS, you'll need a UNIXish cron job or a Windowsish scheduled task running an appropriate application at midnight each day.
Pro tip Do your best to avoid scheduling stuff for precisely midnight. Many things run then. If you wait until a couple of minutes after the hour, your code is less likely to contend with other midnight code.
Related
I am building an event reminder page where people can set a reminder for certain events. There is an option for the user to set the amount of time before they need to be notified. It is stored in notification_time and notification_unit. notification_time keeps track of the time before they want to be notified and notification_unit keeps track of the PHP date format in which they selected the time, eg. i for minutes, H for hours.
Eg. notification_time - 2 and notification_unit - H means they need to be notified 2 hours before.
I have Cron jobs running in the background for handling the notification. This function is being hit once every minute.
Reminder::where(function ($query) {
$query->where('event_time', '>=', now()->subMinutes(Carbon::createFromFormat('i', 60)->diffInMinutes() - 1)->format('H:i:s'));
$query->where('event_time', '<=', now()->subMinutes(Carbon::createFromFormat('i', 60)->diffInMinutes())->format('H:i:s'));
})
In this function, I am hard coding the 'i', 60 while it should be fetched from the database. event_time is also part of the same table
The table looks something like this -
id event_time ... notification_unit notification_time created_at updated_at
Is there any way to solve this issue? Is it possible to do the same logic with SQL instead?
A direct answer to this question is not possible. I found 2 ways to resolve my issue.
First solution
Mysql has DATEDIFF and DATE_SUB to get timestamp difference and subtract certain intervals from a timestamp. In my case, the function runs every minute. To use them, I have to refactor my database to store the time and unit in seconds in the database. Then do the calculation. I chose not to use this way because both operations are a bit heavy on the server-side since I am running the function every minute.
Second Solution
This is the solution that I personally did in my case. Here I did the calculations while storing it in the database. Meaning? Let me explain. I created a new table notification_settings which is linked to the reminder (one-one relation). The table looks like this
id, unit, time, notify_at, repeating, created_at, updated_at
The unit and time columns are only used while displaying the reminder. What I did is, I calculated when to be notified in the notify_at column. So in the event scheduler, I need to check for the reminders at present (since I am running it every minute). The repeating column is there to keep track of whether the reminder is repeating or not. If it is repeating I re-calculate the notify_at column at the time of scheduling. Once the user is notified notify_at is set to null.
I have a .RDL report which I designed in BIDS and have deployed to my report server. The report asks for three parameters before viewing report: Year, Month and Customer ID. The report works great and does exactly what it is supposed to.
While I used to run each report individually because there were 2-3 customers, now there are 30+ customers who receive the report, so I wanted to switch to a more automated fulfillment method to get the reports generated. After doing some research it appears that a using Report Manager to create a "Data Driven Subscription" (DDS) using the "Windows File Share" option gives me the capabilities I need.
As part of creating the DDS, I created a table called [Subscription] which is a table containing one row for each customer receiving the report and has the following columns:
Year
Month
CustomerID
FileName
FileLocation
Overwrite
Format
...so through using the DDS Wizard in Report Manager, I was able to successfully set up a Data Driven Subscription (which is linked to various columns in the [Subscription] table) which creates a new report for each customer in the [Subscription] table, saves [and overwrites, if necessary] it in a location of my choosing as a PDF (specified in [Subscription].[FileLocation], or the FileLocation column of my table for each row), and runs every minute (I plan on changing frequency to once a week, eventually).
This works flawlessly, giving me a new set of 30 reports in the directory of my choosing, with each report having a name I assigned in the FileName column of my table. Exactly what I was looking for.
HERE'S THE PROBLEM: When I update the FileLocation or FileName (or anything, really) in the [Subscription] table - it doesn't pick up the changes right away. Sometimes it doesn't even pick it up at all (for example I updated the [ReportName] column for one customer from Report_711622 to SpecialReport_711622, so that the output file for that customer should be named SpecialReport_711622 while all of the other reports should be called Report_XXXXX [no Special prefix]. But the file name of report for Customer 711622 remains the same!
It's almost like the job only see's what it needs to do once a day, and then does not go back and reference the [Subscription] table until I leave for the night, then when I come back in the morning it picks up the change.
Since I am about to scale this process out to a large customer-base using a different report, I need to be able to make edits to the [Subscription] table and have them get picked up by the Data Driven Subscription immediately (and if not immediately, at least a fixed interval of time that I can adjust, so that I can know 100% when the change will get picked up).
Does anyone know what's causing my lag? How do I change it so that updates to the Subscription table get picked up regularly? I'm also having issues with creating new DDS on other reports (following the exact process outlined above) - I've created the subscriptions, for every minute, and it says they are running and the number of outputs match the number of customers with 0 errors, but there are no files in the drive I specified (or anywhere else I've looked, for that matter).
Any help would be greatly appreciated!
I think the answer lies in the mechanism SSRS uses. There are a few places "lag" can occur.
The subscription is in fact an SQL Agent job which creates a record in the Event table. This table is a queue that SSRS checks to do scheduled tasks.
There is a small amount of time between the moment the subscription creates the Event record and the moment SQL reads it and starts creating the dataset for your DDS. The creation of the DDS dataset takes some time, too. In this time, the subscription will be in the Pending state. If you change anything in the data during this time, The subscription will still use the old data as report parameters. So obviously you will not notice your change until the next scheduled run.
Which brings me to the following: if a subscription is still being run and the next schedule kicks in (chances are, because yours runs every minute), the engine will not execute it, but wait for the next subscription schedule, and so on. So that's another possibility of lag - and cause of missing reports for a certain schedule minute. The subscription processes reports sequentially, one row from your DDS recordset at a time. Again, this takes some time. You can also see that in the subscription window when it says: # of # processed.
I suggest you look at the Event table in the database ReportServer during an execution. Also the ExecutionHistory views (there are 3) may be interesting. A scheduled run shows up as a RequestType = 1 and generates one record for each report. You can see the exact timing and parameters of each report that is run in the subscription. You may be able to extract the data you need to resolve your other issues.
EDIT: Here is a more elaborate guide to DDS data and events
http://blogs.msdn.com/b/deanka/archive/2009/01/13/diagnosing-and-troubleshooting-subscriptions.aspx
http://blogs.msdn.com/b/deanka/archive/2010/02/16/troubleshooting-subscriptions-part-ii-using-the-report-services-trace-log-file.aspx
Could this "Double-Hop" problem be the source of my issues? I'm so stuck on this one!
The Double-Hop Problem - MSDN Knowledgecast
I need to scheduled events, tasks, appointments, etc. in my DB. Some of them will be one time appointments, and some will be reoccurring "To-Dos" which must be checked off. After looking a google's calendar layout and others, plus doing a lot of reading here is what I have so far.
Calendar table (Could be called schedule table I guess): Basic_Event Title, start/end, reoccurs info.
Calendar occurrence table: ties to schedule table, occurrence specific text, next occurrence date / time????
Looked here at how SQL Server does its jobs: http://technet.microsoft.com/en-us/library/ms178644.aspx
but this is slightly different.
Why two tables: I need to track status of each instance of the reoccurring task. Otherwise this would be much simpler...
so... on to the questions:
1) Does this seem like the proper way to go about it? Is there a better way to handle the multiple occurrence issue?
2) How often / how should I trigger creation of the occurrences? I really don't want to create a bunch of occurrences... BUT... What if the user wants to view next year's calendar...
Makes sense to have your schedule definition for a task in one table and then a separate table to record each instance of that separately - that's the approach I've taken in the past.
And with regards to creating the occurrences, there's probably no need to create them all up front. Especially when you consider tasks that repeat indefinitely! Again, the approach I've used in the past is to only create the next occurrence. When that instance is actioned, the next instance is then calculated and created.
This leaves the issue of viewing future occurrences. For this, you can start of with the initial/next scheduled occurrence and just calculate the future occurrences on-the-fly at display time.
While this isn't an exact answer to your question I've solved this problem before in SQL Server (though database here is irrelevant) by modeling a solution based on Unix's cron.
Instead of string parsing we used integer columns in a table to store the various time units.
We had events which could be scheduled; they could either point to a one-time schedule table that represented a distinct point in time (a date/time) or to the recurring schedule table which is modelled after cron.
Additionally remember to model your solution correctly. An event has a duration but the duration is unrelated to the schedule (but an event's duration may impact the schedule by causing conflicts). Do not try to model duration as part of your schedule.
In the past when we've done this, we had 2 tables:
1) Schedules -> Includes recurrence information
2) Exceptions -> Edit/changes to specific instances
Using SQL, it's possible to get the list of "Schedules" that have at least one instance in a given date range. Then you can expand in the GUI where each instance lies.
We are currently developing an application in which multiple entities have associated opening hours. Opening hours may span multiple days, or may be contained within a single day.
Ex. Opens Monday at 6:00 and closes at Friday at 18:00.
Or
Opens Monday at 06:00 and closes Monday at 15:00.
Also, an entity may have multiple sets of opening hours per day.
So far, the best design I have found, is to define an opening hour to consist of the following:
StartDay, StartTime, EndDay and EndTime.
This design allows for all the needed flexibility. However, data integrity becomes an issue. I cannot seem to find a solution that will disallow overlapping spans (in the database).
Please share your thoughts.
EDIT: The database is Microsoft SQL Server 2008 R2
Consider storing your StartDay and StartTime, but then have a value for the number of hours that it's open. This will ensure that your closing datetime is after the opening.
OpenDate -- day of week? e.g. 1 for Monday
OpenTime -- time of day. e.g. 08:00
DurationInHours -- in hours or mins. e.g. 15.5
Presuming a robust trigger framework
On insert/update you would check if the new start or end date falls inside of any existing range. If it does then you would roll back the change.
CREATE TRIGGER [dbo].[mytable_iutrig] on [mytable] FOR INSERT, UPDATE AS
IF (SELECT COUNT(*)
FROM inserted, mytable
WHERE (inserted.startdate < mytable.enddate
AND inserted.startdate > mytable.startdate)
OR (inserted.enddate < mytable.enddate
AND inserted.enddate > mytable.startdate)) > 0
BEGIN
RAISERROR --error number
ROLLBACK TRANSACTION
END
Detecting and preventing overlapping time periods will have to be done at the application level. Of course you can attempt to use a trigger in the database but in my opinion this is not a database issue. The structure that you came up with is fine, but your application logic will have to take care of the overlap.
There's an article by Joe Celko on the SimpleTalk website, over here, that discusses a similar issue, and presents am elegant if complex solution. This is probably applicable to your situation.
A table with a single column TimeOfChangeBetweenOpeningAndClosing?
More seriously though, I would probably not worry too much about coming up with a single database structure for representing everything, eventually you'll probably want want a system involving recurrences, planned closures etc. Persist objects representing those, and then evaluate them to find out the closing/opening times.
This looks like a good solution, but you'll have to write a custom validation function. The built in database validation (i.e. unique, less than x, etc.) isn't going to cut it here. To ensure you don't have overlapping spans, every time you insert a record into the database, you're going to have to select existing records and compare...
First the logic, two spans will overlap if the start value of one falls between the start/end of the other. This is much easier if we have datetimes combined, instead of date1,time1 and date2,time2. So a query to find an overlap looks like this.
select openingId
from opening o1
join opening o2 on o1.startDateTime
between o2.startDateTime
AND o2.endDateTime
You can put this into a trigger and throw an error if a match is found.
I need to implement a feature similar to the one provided by Microsoft Outlook to make your meeting appointment recurrent. I am trying to figure out the optimized Database design that I will be requiring for implementing this feature.
The requirement is something like that each run or task entered by the user will also be applicable for scheduling like a recurrent event - weekly, monthly or yearly. Could you please suggest me the Database model - table structure (with constraints) for storing these details in the DB which can be afterwards accessed by the program to do the appropriate task. Screenshots for some of the possible scheduler details can be found at the following link.
We have a mysql DB running at the backend for storing these details. As soon as the user submits a request, a request id with the details of the request is stored in the table and then a action corresponding to it is taken by the program. More clarification would be like that the users intent is to run a sql script,getting the values and then performing statistical analysis to it. But as the oracle reference DB is dynamically updated by many users, he wants to run it in a recurrent manner and get the analysis done. Note that the mysql db and the ref DB are different.
Please let me know if you require any other details.!
I would suggest storing the details of the first occurence in one table (scheduled tasks) and then the recurance (recurring tasks) details in another.
I might also then be tempted to update the scheduled task table with the next occurance as each task is completed.
As for the Table layout, a rough sketch would be as follows:
[ScehduledTasks]
TaskId (Primary Key)
Description and Details etc...
Start Datetime
End Datetime
[RecurringTasks]
TaskId (Foreign Key)
Frequency : Daily, Weekly, Monthly or Yearly.
DayNo : What Day to run on (1-7 for weekly, 1-31 for monthly, 1-365 for yearly)
Interval : Every x weeks, months etc.
WeekOfMonth : first, second, third... etc If populated then DayNo specifies the day of the week.
MonthOfYear : 1-12.
EndDatetime : The last date to perform
Occurences : The number of times to perform. If this and the previous value are null then perform for ever.
Obvious certain fields would be blank depending on how the task was set up, but I think the above covers all you would need to emulate the tasks in Outlook.