How can I model budget-data for a budget application? - database

I want to create an application which allows Users to budget money they already have into various categories for a given month.
I've already modeled and prototyped handling the data which is tangible; e.g. Bank Accounts, Transactions, Transfers. The problem I am running into is with relating this "real" data (the stuff sitting in your bank, or in your pocket, or on your bank statement) with these fake notions of Budgets (or, as I like to consider them, envelopes).
Here's a quick list of requirements that I've thrown together:
User can manage their Financial Accounts
User can manage their Financial Transactions
User can associate each Transaction with a Financial Account
User can transfer money between Accounts
User can assign available money to a given Budget Category, per-month
User can modify existing Monthly Budget Categories (reduce or increase)
User can view the amount of money remaining for a given Monthly Budget Category
User can view amount of money available to Budget (may be negative)
Money remaining from a Budget Category can carry over to the next month
User can view their Financial Account totals (should not be affected by budget)
User can create Budget Categories as goals that could eventually be closed (e.g. Savings for a new car)
(Probably some other Use-Cases I am forgetting)
The use-cases in bold are the ones I am struggling with.
I toyed with the idea of having a "MonthlyBudget" object, which each transaction could be related to; but this seemed overly-complicated to implement in a database because I'd have to implement a date-range instead of a simple date.
I played with the idea of treating these Monthly Budget Categories as Accounts, and one would simply perform Transfers to them; but then there'd be no way for the User to cross-check their bank statement with the data in the system.
I played with the idea of "fake money" in which Budgets would somehow make use of, thereby separating "real money" and "budget money" -- but couldn't think this through logically.
I'm a bit at a loss on finding a clear and concise way of implementing this, specifically using a relational-database for storage. If anyone has any suggestions or idea, I'd be very appreciative.

The reason why people experience frustration with the budget envelope method is that it ties budget allocations to specific money actually present, whereas money is fungible and can count against the budget, whatever the source. Moreover, when you write a check or swipe your credit card, it may be for a purchase that includes multiple budget items.
A typical commercial budget data model sets up budgets in periods (monthly in your definition) and budget items with amounts. When funds are disbursed, the payment is applied to the appropriate budget item(s), partially or in full. To find out what you have left to spend in your budget, subtract all the applied payments.
If this is for personal finance, people are on a cash basis. However, the same principles apply. So you would have a grocery bill of $220. Maybe $150 of that was for regular food we eat all week, and the other $70 was for a Christmas party. When you come home and enter the grocery bill into the computer, you would want options:
Apply the whole $220 to grocery, because it has to be made up somewhere;
Apply the $150 to grocery and apply the $70 to seasonal entertainment;
Apply the $150 to grocery and put the $70 aside, because I haven't set up a seasonal entertainment budget yet. We don't want to make the user stop the whole process to create more budgets in order to enter the grocery bill, or soon s/he won't be entering the grocery bill faithfully any more because it is just too much work.

Related

How to secure money (USD) balances in a database

I was wondering how people are securely storing money balances in a database. E.g how do you make sure that the database administrator does not modify balances or transactions? How do you make sure that the code that does a transaction not accidentally or intentionally by a rogue employee does not work correctly.
Banks, PayPal and any other apps that hold balances in USD or any other currency should have this problem
All the banking packages I've worked with store the balance with the account entity. Calculating it on the fly from movement history is unthinkable.
The right way is:
The movement table has an 'opening
balance' transaction for each and every account. You'll need
this in a few year's time when you
need to move old movements out of the
active movement table to a history
table.
The account entity has a balance
field
There is a trigger on the movement
table which updates the account
balances for the credited and debited accounts. Obviously, it has commitment
control. If you can't have a trigger, then there needs to be a unique module which writes movements under commitment control
You have a 'safety net' program you
can run offline, which re-calculates
all the balances and displays (and
optionally corrects) erroneous
balances. This is very useful for
testing.
Some systems store all movements as positive numbers, and express the credit/debit by inverting the from/to fields or with a flag. Personally, I prefer a credit field, a debit field and a signed amount, this makes reversals much easier to follow.
Notice that these methods applies both to cash and securities.
Securities transactions can be much trickier, especially for corporate actions, you will need to accommodate a single transaction that updates one or more buyer and seller cash balances, their security position balances and possibly the broker/depository.
From smirkingman answer on Database design: Calculating the Account Balance

UML use case diagram for cinema equipment retailer

I have been given the following scenario :
HyperAV is a retailer of home cinema equipment. They sell a variety of products including televisions, speakers, amplifiers, Blu-ray/DVD players and cables. The company has its head office in Stockport and 5 retail branches around the UK (in London, York, Cardiff, Manchester and Newcastle) and a large warehouse in Birmingham.
Due to the specialised nature of the products most sales are made in the shops which also have demonstration facilities allowing staff to show off the products to customers before they buy. However, the shops can also take orders over the telephone. The company deals with a number of suppliers who deliver items to both the shops and the warehouse. Limited space is available in the shops, so large numbers of items are stored at the warehouse and sent to the shops when their stock runs low.
The company’s buyer and stock controller are based in Stockport and work together to ensure that each branch has an adequate stock level of fast-selling items. If a shop takes an order for a product that it does not hold in stock, payment is taken and the item is sent to the shop from the warehouse. If the warehouse does not have a product in stock, it is ordered from the supplier by the buyer.
From this scenario I have been asked to draw a use case diagram.
I have received feedback but only to an extent where I have been told it is slightly incorrect. I would like to know if anyone can see what is wrong with it or how i can improve it in anyway?
I will not go and analyze what is right/wrong with your business case, but here are a few remarks:
Do not use Generalization with UCs. Each UC shall be a unique added value the system under consideration (SUC) delivers to the actor. If you have Generalization this means your UC is not unique. E.g. Deliver product: these are two absolutely separate UCs. They use a delivery service. But that's a UC for another SUC (namely the delivery service).
Avoid the use of <<include>>/<<extend>> as they indicate the use of functional analysis. UCs are about synthesis which is the opposite of that.
Use verb-substantive to name your UC. Order for example is not a UC.
Think about the "use" in UC. What is the added value it returns to its actor? If that is not of a real use, it's not UC. Process payment is an administrative task, not a UC. So what is the use behind this?

Designing a database for stock control

Having a few issues with my database design. I have designed my system like the following image
As you can see it is a pretty basic system to a point. A user can create a supplier by adding supplier details. A user can then add a product and link it to a supplier. Thats the pretty straight forward bit (I hope!). Now I will attach my database design which should hopefully cover what I have mentioned.
So a supplier can have one contact (person within the suppliers company the user of my system will contact) and a supplier can have one to many products.
He is the part I can't figure out. Twice a week, the user of my system will receive stock from all their suppliers. When they receive this stock, they should go into the update stock screen within the application and input the amount of stock they have received for a certain product. I have added a products_stock table which should hopefully put me on my way to cover this aspect (I think it is missing a lot though).
The last screen however is a display of predicted stock. Lets say for instance on the day my products are delivered, I receive 10 units for Product One. I will then manually count the number of units I have left from the last order for Product One (say 2) and update the stock count for Product One to 12.
This means, that really, I only needed 8 units between the two deliveries for product one. The predicted stock screen is supposed to show the predicted stock levels I should place an order for, for a particular product, over a specified time period. So if 8 units was the average stock sold for product one per week, if I wanted to see how many units I should order for product one for a month, it should display about 32 units.
This is not supposed to be a complex system, it should have this manual aspect to it. I have designed the database up until a point, I was hoping I could get some suggestions regarding the products_stock table and how I can handle stock predictions for a specific period of time (if I maybe need additional tables).
Any advice appreciated.
Thanks
Inventory is more like a view and not a table. Inventory is really a series of movements of goods between locations, as well as periodic counts / adjustments.
Inventory is complex. You should play with some inventory software and read some data modeling books.
Use the concepts of Locations (real and virtual) and Movements (a movement should be its own entity).
Item smashes? Move it from its inventory location to the "damaged" location
Item went missing? Move it from inventory to the "ether" location
Found a random Item? Move it from "ether" to inventory
Sold an Item? Move it from inventory to "sold"
Bought an Item? Move it from purchased to inventory
Some other things to keep in mind:
You could sell something, and it's returned, and you put it back in
inventory
You could buy something, but it ain't right, so you send it
back to the seller
You could sell something that you don't own (on
consignment, or not in inventory yet)
You might have something in
inventory that is not currently for sale.
I won't get into the accounting aspects of inventory :)
One possible approach:
Have a separate "stock item" record for each unit received. When it is sold, record the date of sale in this record.
Then if you want to know how many items were sold in a given time range, just count the records with sold dates in that range, like select count(*) from stock_item where product_id=#product and sold_date between #from and #thru. If you need to keep track of items lost to spoilage, theft, whatever, then you might have a status flag of some kind that says whether it's in stock, sold, destroyed, whatever, and also the date of that status.
If the number of units that pass through is large and there's no other reason to keep individual stock records, you could just have "daily sales" records instead, with a date and number sold that day. Same idea.

How can I charge sales tax depending on merchant?

I have a table of all zip codes (and states) and sales tax rates and a table of merchants. I am trying to store which merchants charge sales taxes in which states. I was planning on adding a table which maps merchants to states they charge taxes in. However, there are a bunch of exemptions for different categories. For example, New York doesn't charge sales tax on clothes if the total is under $110, and Vermont doesn't charge sales tax on clothes at all.
Can I store something like that in a database in a clean way, or should I create a messy helper file that includes these rules?
You're in for a world of hurt if you try to roll out your own billing from scratch. There are also city, county, special purpose district, and transit authority taxes with various exemptions rules depending on where you are buying from.
Recommend using third party billing — for a lot of reasons, mostly outside of the scope of SO. With third party billing, you just need to concentrate on classifying the items correctly.
Is your intent that you will use this database to calculate sales tax, or that it is purely for reference/information?
If you're using it to calculate the tax, then a "messy helper file" would be, well, very messy.
If you're trying to deal with sales taxes from many states, then as Buddy says, this is a huge job. I had a little business in Ohio for a while and I was only selling one product and only had to deal with Ohio taxes, and it was still a complicated mess because of all the different taxing entities and different rates. Worst was the sales tax to support mass transit in Cleveland, as the places where this tax was imposed did not follow any simple geographical boundaries, that is, you couldn't just say "county X, yes or no" or anything like that. The only practical way to tell was to submit an address to their web site and they'd tell you if it was within their boundary. If you have to deal with all 50 states I'd be terrified at all the special cases that are likely to come up. So if you can find some third party software to do this, I'd seriously consider it. Somebody who has the resources to study the tax laws of every state and figure them all out and keep current on them.
Failing that ... I'd say you'd have to go through every state's laws and figure out all the cases that you have to deal with. Many states exempt some categories of products, like food and clothes. Some have different rates for different products, like surtaxes on luxury goods. I hadn't heard of an exemption up to a certain amount before, but apparently that's something else to consider. I'd say you have to find out what all the rules are, what data you need to support each, and build a monster table of all these rules. Presumably the table would include columns for applicable taxing entity, product category, rate for this category (possibly zero), and dollar threshold at which the rate applies. Maybe you'll discover other things.

Database design for a wedding photography booking system website

I'm really stuck on the best way to implement this database.
Here is my problem: The database is to store information on wedding photography clients.
A user can sign up to my site, enter the details of their wedding and get their own "wedding profile page". They can do this without having to have us shoot their wedding.
At any point the user can book a meetup, wedding, or engagement shoot. The website will check if we are available. (weddings take preference over meetups so a client that wants to book a wedding on a day we have a meetup, the meetup will be flagged for a reschedule)
We must also be able to book days off. On these days a wedding/meetup/engagement shoot can not be booked.
engagement shoots cost and upfront fee. With weddings, a deposit is due within 14 days or the date is freed up again. Meetups are free.
I am so stuck with how to implement this system. I just keep going round in circles, the best way I can think is to have a "dates" table, that links all the other tables but I'm sure this is not the most efficient way.
I think what is putting me off is the fact that there can be multiple weddings on the same day (for people who just want a wedding profile), but only one BOOKED wedding per day.
So have I got this completely wrong? or do I store all appointments in one table and use a "type of appointment" table.
SO SO Stuck, I hope you can help me!
P.S. I have missed most fields out to make it simpler to understand.
Keep it simple to begin with. You've identified many of the nouns that should correspond to entities:
USERS
WEDDINGS
ENGAGEMENT_SHOOTS
MEETUPS
UNAVAILABLE
DATES
PAYMENTS
I'd suggest that WEDDINGS, ENGAGEMENT_SHOOTS, MEETUPS and UNAVAILABLE are all type of bookings. You could have just:
USERS
BOOKINGS - this has a date and perhaps a status
BOOKING_TYPE (wedding, meetup, engagement_shoots, unavailable)
PAYMENTS
You may wish to package up all on the things a use has bought relating to a single wedding into a TRANSACTION entity etc which will allow a single payment to be mapped to multiple bookings. When one of your staff isn't available they could have a booking of type holiday etc.
There may be 2 types of USERS - your photography staff who are assigned to a booking and your customer.
Based on the status of the booking, eg. CONFIRMED, PENDING, COMPLETED and the date your business logic could send out payment demands, followups etc.
Create a simple model and start adding data you will soon see the gaps and issues if any. You should have test cases up front to ensure that the data model supports all the scenarios for your application, best to do this with a set of use cases.

Resources