database work flow analysis - database

I have analyzed my as below and I have two point I am confused about
1- currently when I insert an items within orders I give order_ID as a PK
so each item within the order as its own PK... and same customer_id (FK) for all Item within the order so ... in that case the invoice number is same as the customer_ID
Is that what should think goes on or there is something wrong with this work flow ?
2-in some cases I don't need to record the customer information I just want to
insert the orders without their customer info.. I don't have clear idea about how think should happen :S
3- IF I want to apply a discount on some customer orders where the discount should I allow user to able to apply on the item per orders level ?
or on the whole order ? and where the discount column should be stored

1 - This design seems fine for the problem. You are stating that for every product ordered, this is the customer line. You can pick the ID, name, tax/fiscal number, address, etc.
2 - If you don't need any kind of customer information, make the customer_id on the Orders table accept NULL. It is the cleanest way to do it.
If for some reason NULLs are not an option or you want to keep on the database some basic anonymous customer data, you can create a line on customers for anonymous users (Ex.: ID: 1 / Name: ANONYMOUS ...) and place that ID on the order line.
3 - Placing the discount per product ordered might be the better idea.
If you want to apply a discount for the complete order, you just need to place that discount on every single order line.
If you want to apply a discount for a single product, you just need to place that discount on that product line.
If you want to apply a discount for a single product with a limited ammount of quantity (Ex.: Discount of 50% but limited to 1 purchase), and the customers buys more than that limit, you just need to place 2 orders for the same product. One with the discount and max quantity and the other without discount and the rest of the quantity.
Placing this on the order level wouldn't work for single product discounts.
This were answers to your questions. I would also question your design in points like:
If the customer changes address, is your order supposed to change too? If not, you should use the normal approach for orders, which is to have a order header table, with fixed information, like the address and the foreign key to the customer, and a order line table, like your orders line, but with a foreign key to the order header. That also avoids repetition.
Are you expecting up to 2 phone numbers? If you do, the design is ok. If you don't know how many phone numbers to expect, maybe a table with phone numbers, with foreign keys to the customer might be a better approach.

Related

Laravel (and not only) Many-to-many relationship Belongs-To-All

I have two tables. 'Products' and 'Discounts'.
Then I create a joining table 'discount_product' for Many-to-many relationship. So far so good.
Now if I want a discount to belong to ALL of the products I have to make insertions into the joining table for as many products I have. That means that having 10000+ products I'll have to insert 10000+ rows for one discount into the joining table? And that's only for one discount! What if I have 1000?
That's compelling me into returning to the old (wrong) way of doing it when I just have a column 'product_ids' in the 'Discounts' table with something like this '1|2|4|7|23|...' (or '*' for 'belongs to all') and then make a small piece of PHP code to check if discount belongs to all or to some products. I know it's wrong way of doing it. So is there a better way to make this properly?
Structure:
**products**
id
description
price
**discounts**
id
procent
value
**discount_product**
product_id
discount_id
I propose to try to change some business logic.
If the discount is not in the discount_product then this means that it applies to all products.
If the discount is in the discount_product then it means that it works only for a certain product.
If you need to ensure that the discount is not applied to any product, add the field is_active in discounts.
It's just my thoughts.
I believe that sometimes it is useful to denormalize the database because of optimization, and I would do as you suggested with the product_ids field.

Order/Invoice/Payment database modeling

I am designing an e-commerce website that has the following scenario:
A customer can purchase items and create an order.
The order may have unknown fee that will be added after the customer
pays the total amount of the items. That is, the customer pays
certain amount first. The order adds some fee and changes the total.
And the customer pays again for the difference. But the two (or
more) payments are associated with the same order.
(Optional) The customer can submit a single payment for multiple
orders.
Currently, I have an Order table and each order may consist of multiple OrderLineItems (simplified schema):
Order
=====
customer
line_items
total
status
OrderLineItem
=============
price
quantity
order
product
A payment is associated with an order (simplified schema):
Payment
=======
order
payment_account
total
result
It seems to be very hard to support the multiple payments for a single order scenario in the current implementation. I reckon that I have to introduce immutable invoices in the system, and the payment should be associated with an invoice instead of an order. However, I would need some help with the order/invoice/payment modeling for the above scenario. Some specific questions I have:
An order and an invoice look very similar to me (e.g. both have
items and totals). What is the major difference in typical
e-commerce systems?
How should I model invoices for my scenario? Should I have
OrderLineItems for an Order AND InvoiceLineItems for an Invoice?
Some preliminary thoughts: I will have multiple invoices associated
with a certain order. Whenever the order changes the total, I have
to somehow calculate the difference and send a new/immutable invoice
to the customer. Then, the customer can pay and the payment will be
associated with the invoice.
Would love to hear some advice. Much appreciated. Thanks!
There are a lot of questions here, I'll try to address as many as I can. A lot of the issues are the business model rather than the data model.
Firstly, you are right that you need an immutable invoice. Once an invoice is created you cannot alter it, the standard way of handling a change in invoice is to issue a credit note and a new invoice.
Think about the relations between the tables: the Order does not need to hold the lineItems as these are referenced the other way, i.e.
Order
=====
orderId
customerId
status
OrderLineItem
=============
orderLineItemId
orderId
product
price
quantity
So to view the order you join the tables on orderId. There's also no need to store the total as that is calculated from the join.
Try not to duplicate your data: your invoice will reference orderLineItems, but not necessarily the same ones in the order. For example, the customer orders an A and a B, but B is out of stock. You ship A and create an invoice that references orderLineItemId for A. So your invoice tables might look like:
invoice
=======
invoiceId
status
invoiceLineItem
===============
invoiceId
orderLineItemId
quantity
In other words there's no need to have the details of the item. You may be wondering why you don't just add an invoiceId to the orderLineItem table - the reason is the customer might order 10 of item A, but you only ship 8 of them, the other two will go on a subsequent invoice.
Payments are not made against orders, they are against invoices. So your payments table should reference the invoiceId.
Then you touch on reconciliation. If everything was perfect, the customer would make a payment against a particular invoice, even if a partial payment. In reality this is going to be your biggest headache. Suppose the customer has several outstanding invoices for amounts x, y and z. If they make a payment of p, which do you allocate it against? Perhaps in date order, so that if p>x the remainder is allocated against y. What if p=z? Perhaps the customer is intending to pay z now but is disputing y and has mislaid x? How you deal with these sorts of things is up to you, but I can say that most invoicing systems do it very badly indeed.

Data modeling : gas station managing

I need to create a database to manage a gas station.
I'm thinking of a basic product inventory and sales data model, but it need some changes.
See http://www.databaseanswers.org/data_models/inventory_and_sales/index.htm. This is how they proceed: the manager keep tracks of the inventory and sales twice a day, each time a gas pump attendant is in charge, and takes the responsibility of the sales.
How can I keep track of this ?
Using the Model that you provided you could use the first Model as reference:
And I would use all the six (6) tables namely:
1) Products
2) Product_Types
3) Product_In_Sales
4) Sales
5) Daily_Inventory_Level
6) Ref_Calendar
But I had to make some changes by alteration and adding:
First I need to include SalesPerson table that would have at least the following fields
1) SalesPersonID
2) Lastname
3) Firstname
4) Alias
In line with that I therefore need to add SalesPersonID as Foreign key in
my Sales table.
Now since you want to have twice a day Inventory then you could approach in many ways
you could add single primary key for Daily_Inventory_Level table or you could add a new field named Inventory_Daily_Flag which has either only the value of 1 or 2. If 1 that means that's the first inventory and if 2 that means that's the second inventory for the day. And that means by the way that you're Primary and Foreign Key at the same time would no longer be just Day_Date and ProductID but also Inventory_Daily_Flag for Daily_Inventory_Level table.
And also in line with that, that means you need to also to add a field in your Product_In_Sales like FlagForInventory with Boolean as Data Type.
So, let's say a Supervisor came in to do the first inventory, then the products sold
in Product_In_Sales for the day would be flag as True for the FlagForInventory and
then would be transferred to Daily_Inventory_Levels with Inventory_Daily_Flag field
as 1 to indicate as the first inventory and of course the Level also would be updated.
And so when the days end and the 2nd inventory is to be executed then those
sales for the day from Product_In_Sales table whose FlagForInventory is false then
it would be flag as True for FlagForInventory and then transferred again to Daily_Inventory_Levels with Inventory_Daily_Flag as 2 indicating the second inventory.
And of course you need to update the Level as well.
Does it make sense? If not I could always change the approach? ;-)

Help with table relationships

I need a little help designing a database that a bar would use for drinks. My app handles drink orders in 2 ways: A customer can order drinks and pay right away, or they can start a tab. This is my table relationship so far:
Table Order: Table Tabs:
------------ ------------
[PK] OrderId - 1 [PK] TabId
ItemName / TabName
QtyOrdered / Total
TabId *- PaymentType
Archive
Its setup so 1 tab can have many drinks on it. Thats great for tabs, but customers can choose not to setup a tab. My question is, how can i modify these two tables to support that? Or do I have to create a new table?
Thanks in advance.
Your "item" is the order line-item.
"My brother and I will each have a Guiness and his wife would like a gin-and-tonic."
There are three (EDIT: items, but two) line-items on that order. To identify them as part of the same order [if you should need to do so], you would need two tables:
the OrderHeader
(orderheaderid, orderdatetime, customerid)
and
the OrderDetail
(id, orderheaderid, drinkid, howmany, extendedprice, paymentamountapplied).
If you do not need to identify the drinks as belonging to the same order, you could abandon the two-table structure, but then you could have only one kind of drink per order.
ORDER
orderid, orderdatetime, customerid, drinkid, howmany, extendedprice, paymentapplied.
Extended price is howmany * the drink's price at time of the order. You store this value in your order table so you can change the price of the drink in the DRINKS table without affecting the tab amount owed (in case the tab lifetime is longer than a day -- i.e. customers can run a monthly or quarterly tab).
HowMany can default to 1. The amount owed on a drink line-item is (extendedprice - paymentamountapplied). PaymentAmountApplied defaults to 0 (i.e. default is to run a tab).
If you do not need to track the kind of drink being ordered (i.e. you don't care to use your database to discover that on Tuesday nights you sell a lot more gins-and-tonic than Guinesses, for some reason):
ORDER
orderid, orderdatetime, customerid, ordertotal, paymentapplied.
Your barkeep would simply enter the total amount of the order, calculated outside your system, without reference to a DRINKS table in the database -- maybe the barkeep would look at a chalkboard on the wall.
You need a CUSTOMERS table, a DRINKS table, an ORDERSHEADER table, an ORDERDETAIL table (each drink on the tab is a line-item). You could/should have a separate PAYMENTS table. And you would allocate payments to the line-items of the ORDERDETAIL (your tab). The "tab" is the set of all line-items on the order(s) that have no payment applied to them.

db design questions (how to deal with groups of products)

I would be grateful if somebody could help me to find an elegant solution to this database design problem. There is a company with a lot of different products (P1,P2,P3,P4) and a lot of customers (C1, C2, C3, C4). Now they have a simple database table to deal with orders, something like
20101027 C2 P1 qty status
20101028 C1 P2 qty status
Now I would like to create groups of products ( eg. (P1+P3+p4) and (P2+P3)) that could be purchase together for a reduced price. What is the best way to represent such groups in a database system? Dealing with these groups as individual products doesn't work, because I need the functionality of replacing, adding or removing products from the groups. So I need to keep the currently given table of products.
Thanks for reading. I hope I will get some help.
Add a new table product_group_promotions, with an ID, name and discount price. Then create a table product_group_promotions_products that links products to product group promotions. This will contain a product group ID and a product ID. This way, you can place one product in multiple groups, and let groups contain multiple products (of course).
Jan's answer is correct but incomplete.
You'll also need start and end dates of the promotion. You'll probably want to enter next week promotions so they are ready but not apply them until appropriate.
Discount price may not be enough either. You also will need to get business rules from business people as to how to apply the discount. It could be a percentage or a free item or a fixed amount. If a percentage do you distribute the discount evenly, proportionally, on the cheapest product, the most expensive? If a free item, which one in the set is free. It could also be a fixed amount, $10 off if you buy x, y, and z. Is the discount applied more than once. If someone buys 5x of P2 and P3 do they get the discount on all of them or just the first ones. Is there a limit over a time period. As in the past example, if you don't give me the discount on all 5, I would just fill out 5 orders of 1 each and get the discount you were trying to prevent. If so you'd have to go back through previous purchase by that customer to see if they've received that discount.
You can see how ugly this can get. I would clarify with the business EXACTLY what they plan to use this new feature for and run through these use cases with them.
As Q, asked, if the basket of purchased items is large enough there could be more than one discount possible. Do you have to determine what to give, do you present a list of choices back to the UI... and the recalculate.
This is why I have mercy on department stores who screw this stuff up. It's not simple.
On the surface this is simple sounding but in reality it's very complex.
"Dealing with these groups as individual products doesn't work, because I need the functionality of replacing, adding or removing products from the groups."
Here are several things you need to look at:
Current Inventory vs Past Orders
How do you deal with Price Changes on P1, P2, P3
How do you handle adding a new product or products to an existing group
How do you handle removing a product or products from an existing group
In my opinion you need two sets of tables.
Tables that make up your current inventory
Tables that record what customers purchased (historical data tables)
If you need to reconstruct a customers purchase from six months ago, you can not rely on the current data givin the fact that a grouping may not look the same today as it did six months ago. So, if you do not already have a set of historical data tables for customer records then, I recommend you create them.
With a set of historical data tables that house what was bought by the customer you can pretty much do what every you want to the current invetory data. Change prices, regroup products, make products obsolete, Temporarily suspend a product, etc.

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