I have a database and i need to create a table and insert in a column or columns the real time.
i will explain what exactly i want so maybe you can help.
I am making a game so i need with the pass of time a user to gain coins.
For example if the real time is 12:00 am i want in 12:15 the users to gain 50 coins (so a variable inside the database will change automatically after the pass of time), then in 12:30 they gain 50 coins etc.
and all that will happen even if they are online or offline. (i want database to work all time!)
In MySQL, the current time can always be retrieved by using the expression NOW().
Now suppose you want each player to get coins at a rate of 200 per hour. This happens to be one coin every 18 seconds; that's important because we will use integer arithmetic.
Make yourself a table user with these columns in it. I suppose you can also put other columns it it too.
user_id INT
current_coin_balance INT
last_autopay DATETIME
Then, every so often, run the following query:
UPDATE user
SET current_coin_balance = current_coin_balance +
ROUND(TIMESTAMPDIFF(SECOND,last_autopay, NOW()) / 18),
last_autopay = NOW()
If you wish you can add a WHERE clause, to only update some user or users in any given run of the query. Without the WHERE clause the query will handle all the users.
This will work out the number of seconds since the most recent payment and divide by eighteen to get the number of coins. It will then credit the user's balance and record the time when the payment was made.
It doesn't matter how often you run this query for any particular user. You can run it every time a user's record is touched, or every 15 minutes, or whatever you need.
You can run it as a so-called MySQL event (batch job) if you like.
Related
I need to know how many times a page is viewed in a specific timeframe, say the last 30 days. In the database there is a PageViewCount field so every time the page is viewed, the PageViewCount increases, but there is no timestamp in the database of when this occurs.
I know there has to be a simple solution to this, but I am having a real hard time wrapping my brain around it.
As it is stated, it is impossible to query for such a value. Consider the following equivalent example: I have some coins, for a total of $3.50 and I don't track the movements of the coins. How much money did I had yesterday?
You should have a daily procedure that stores the current PageViewCount with the current date in another table and then simply query that table.
I am stuck with a problem. In an app's db, I am having a schedule table which will store user provided schedules. E.g
Daily
Every Week
Twice a Week
Every 3rd (or any user chosen) day of week
Every Month
Twice a month
Every x day of month
Every x month of year
And so on. These schedules will then provide reference point to schedule different tasks or identify their repeat-ance.
I am not able to think of a proper database structure for it. The best I can get is to have a table with following columns:
Day
Week
Month
Year
type
Then store the specified schedule in the related column and provide the type.
e.g Every week can go like 1 in week column and 1 (designated value for repeating whole) or something like that.
The problem with this approach is that this table is gonna be used very frequently and the data retrieved will not be straightforward. It will need calculation to know the schedule type and hence will require complex db queries to get each type of schedule.
I am implementing it in Laravel app if that can provide any other methodology. It's a SAAS app with huge amount of data related to the schedule table.
Any help will be very much appreciated. Thanks
I suggest you are approaching the problem backwards.
Devise several rules. Code the rules in your app, not in SQL. When inserting an event, pre-fill a calendar through the next 12 months with all occurrences of the event. Every month, go through all events and extend the "pre-fill" through another month (13 months hence).
Now the SELECTs are simple and fast.
SELECT ... WHERE date = '...'
has all the events for that day (assuming it is within 12 months).
The complexity is on inserting. But presumably you insert less often than you select.
The table with the event definitions would be only as complex as needed for your app to figure out what to do. Perhaps
start_date DATE,
frequency ENUM('day', 'week', 'month', ...)
multiplier TINYINT, -- this lets you say "every second week"
offset TINYINT, -- to get "15th of every month"
Twice a week would be two entries.
Better yet, there are several packages (in Perl, shell, etc) that provide a very rich language for expressing event-date-patterns. Furthermore, you may be able to simply 'call' it to do all the work for you!
I am looking for a way to create a View that when queried will automatically only retrieve new records since the last query. My tables have a timestamp field for all entries, so for a simple example I can
SELECT * WHERE timestamp >= 'blah'
but I don't know how to determine what blah should be from the last query. So if the View was queried at 11:00 and then again at 12:00, the query at 12:00 should only return records added since 11:00. And so on... This all needs to be accomplished in the View, the end user should simply be able to query the View and get the results.
Is this possible?
There are two ways:
Store last access date time in database per user persistent session
table, if you have one. On next view call to database, use the
previous latest access time in the session to filter rows starting
from.
Store last access date time in user virtual session at client
environment. On every call to server, send last access date time as
well. So that server uses it to filter rows starting from.
I prefer to use second option that process won't write any data in database tables.
As there may be an unread record that slips through undetected (say it came less than a second since the last one accessed, so it has the same timestamp), set a column to auto increment (typically labelled id) and check for entries using it e.g. in PHP save the last accessed record in a $lastId variable, and use:
$sql="SELECT * WHERE `id` > '$lastId'";
I'm trying to help a taxi company. The problem is that they have a credit card machine that takes payments, and has its own database entries, and there is a completely separate database that has a list of entries such as pick up time, and drop off time.
I need to match the database of trip entries to the credit card purchases, and the only way to do this is by matching which vehicle is running the transaction, and looking for a time CLOSE TO the DROP OFF time and see if it's a match. It's not ideal.
So, I am trying to compare two times in yy-mm-dd hh:mm:ss format. They need to be plus or minus 5 minutes of each other. How do I do this in MYSQL?
I thought SubTime and Addtime would work, and it seemed to, but then I got wierd results.
SELECT * FROM completedtrans WHERE DrivID = 128 AND TransTime BETWEEN SUBTIME('2013-06-20 16:53:06', '0 00:05:00') AND ADDTIME('2013-06-20 16:53:06', '0 00:05:00')
Here's an example of one of my searches. Can anyone tell me what's wrong with it? It's supposed to search 5 minutes before and after that particular given time. I can't simply write the time, because the query is automatically generated through php code.
I'm working on an app that is partly an employee time clock. It's not too complex but I want to make sure I head in the right direction the first time. I currently have this table structure:
id - int
employee_id - int (fk)
timestamp - mysql timestamp
event_code - int (1 for clock in, 0 for clock out)
I've got everything working where if their last event was a "clock in" they only see the "clock out" button and visa-versa.
My problem is that we will need to run a report that shows how many hours an employee has worked in a month and also total hours during the current fiscal year (Since June 1 of the current year).
Seems like I could store clock in and outs in the same record and maybe even calculate minutes worked between the two events and store that in a column called "worked". Then I would just need to get the sum of all that column for that employee to know how much time total.
Should I keep the structure I have, move to all on one row per pair of clock in and out events, or is there a better way that I'm totally missing?
I know human error is also a big issue for time clocks since people often forget to clock in or out and I'm not sure which structure can handle that easier.
Is MySQL Timestamp a good option or should I use UNIX Timestamp?
Thanks for any advise/direction.
Rich
I would go with two tables:
One table should be simple log of what events occurred, like your existing design.
The second table contains the calculated working hours. There are columns for the logged in and logged out times and perhaps also a third column with the time difference between them precalculated.
The point is that the calculation of how many hours an employee has worked is complicated, as you mention. Employees may complain that they worked longer hours than your program reports. In this case you want to have access to the original log of all events with no information loss so that you can see and debug exactly what happened. But this raw format is slow and difficult to work with in SQL so for reporting purposes you also want the second table so that you can quickly generate reports with weekly, monthly or yearly sums.
Is MySQL Timestamp a good option or should I use UNIX Timestamp?
Timestamp is good because there are lots of MySQL functions that work well with timestamp. You might also want to consider using datetime which is very similar to timestamp.
Related
Should I use field 'datetime' or 'timestamp'?