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I'm building a php web app that requires to create an invoice, where its ID must be incremented (e.g: 15235, 15236, 15237,...etc). It all works fine with 1 user creating the invoice. The the issue arise when there are more than 1 users hitting the create button at the same time. Supposedly the next incremented ID is 15230, and having 3 users hitting the create button the same time, the app will return 15232 to all 3 users.
FYI, I store the last used ID in a database and increment it when users create an invoice.
Does anyone has any solution? Your suggestion is much appreciated.
Simply use built-in mechanics and define ID field as AUTO_INCREMENT.
You can read more about that here.
After that just skip ID in your INSERT queries and database will take care about that for you.
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My goal is to add pictures inserted by user into a database. So I'm trying to set their names to the date of their creation. The format is "day.month.year hour.minute.second". But I'm facing the problem that the only one picture is added to the catalog. I'm thinking that the reason why it happens is because the script runs too fast for a second to pass.
And that made me think if this is a good idea to name pictures this way.
I started to assume that maybe I need to use some kind of library to manually add a second to every next picture's name.
But before doing that I decided to go ask somebody more profecient than me in order to undesrtand whether I need to do it this way or maybe there's a better one
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I would like to know how I can create a list of top donors, in which the user who donates the most is in the first position of the list.
In order to donate, you must be logged in
How can I do something like that using php and mysql?
This is only how much i understand your question.
First you need to create table for donors which the storage of their data, and 2nd is to make table for donate which holds the donator.
Then to sort the donator by donated the most, just use COUNT sql query to get the highest donate number.
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If the user submits details I will be able to save it in mysql but how can I get only those details on screen. The latest one. Suppose there are millions of users there might be some disturbance for slecting from mysql as so many users submit at a time. So can I any one suggest me how can I overcome this
If you want to get the details of that specific user you can give some kind of token generated randomly or UUID to this user when he enters the page and after that you will be able to do a SELECT with WHERE clause to get this information in a easy way or if you want get the last one from your table maybe you can use LAST() on mysql SELECT LAST(columnName) FROM Table;
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I have a database / systems question.
Say you have a CMS system done in PHP and Mysql
When you have users who edit their details, do you just update their row with the changes or do you keep a history for example by updating their row by setting the column 'status' = H (For History) and insert new row with all the old & new changed details with column 'status' = A (For Active) and that becomes the primary row?
I would just like to know what other developers do?
I'd keep a history for audit purposes but I'd move old records to a history table to prevent problems with primary ids. I wouldn't keep old records in the same table as current, that's just too much redundant data.
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I need to create a quiz site and I'm not sure about how should I proceed with statistics. The site needs to track each users progress (which answer was answered how, how many time does it take to answer each question etc).
Should I create a new table (let's say 'statistics), and should I create a new row each time a user has finished a quiz? So, statistics:
user_id
quiz_id
answers (in serialized form, because the amount of questions is variable)
time_of_answer (same as above)
points_for_each_answer (same as above)
Wouldn't this be too slow, if the admin wants to check some stats, let's say: how many users have correctly answered the question #2 under the 3rd quiz?
Don't serialize answers if you need them as a real entity - just give them a quiz_id foreign key so you know to which quiz they belong, use proper indexes, and everything will run smooth.