its about internet shop program.
Customer, products, Order, and supplier is involved.
How to implement that the customer can be a product supplier in the same system ?
How to design it and what is the idea to impelemnt it ?
this is what i have tested but im not sure if i did right.
I believe that you are on the right path. The customer entity is different from the supplier entity. As a result, if a user is both a customer and supplier, he will have both a supplierID and CustID. This is shown in your diagram by the relationship with the User entity. However, the Customer entity will need to have a foreign key to link it to the User table. this will likely be UserID. Same for the Supplier entity.
Related
I´m starting in database schema. I don´t have experience in it.
I am thinking of a platform for customers to have access to the types of products that suppliers offer.
So, I would like to know how to keep the database schema following the tables and their relationships.
The customer will be registered in the system and he will have access to suppliers and their products.
Costumer>>>>>>>>>Product>>>>>>>>>Supplier
I already thank anyone who can help.
greetings
Ed
Based on the data you've given.
You would have a Product table, a product can be sold by one or more supplier. So you would have a Supplier table. Since this is a many to many relationship you would have a cross reference table
Customer's wouldn't be related to Products or suppliers.
Customers generally don't have a direct relationship with Products. Generally, customers create orders, composed of multiple products.
So customers typically have a one to many relationship with an 'Orders' table. The Orders table has a one to many relationship with an OrderItems table. That table might store quantity, color, etc, and has a many to many relationship with the Products table.
Of course, that's just the typical entity relationship. Without more information, it's hard to know if it meets your needs or not.
I want to create a database following the following specifications:
A well known bicycle company stores its data in a special database.
Company has customers and
products.
All customers have a unique customer_id.
Customers are categorized as foreign customers or domestic customers. A customer must
be foreign or domestic, and can not belong to both of the categories at the same time.
Foreign customers are identified by their unique id, currency, company name and address
composed of city state and zipcode.
Domestic customers are identified by their unique id, name and address. Domestic
customers may have more than one address information.
Products are identified by unique product_id, model, type and price.
Only two type of products are produced in this company. These product types are Bike and
Mountain Bike.
Each bike has color and cycle attributes.
Each mountain bike has cycling team attribute.
A product may belong to at least one of this types. Moreover it may belong to both of them
at the same time.
Customers may request products. And a product may be requested by more than one
customer, also it may not be requested by any customer at all.
When a product is requested or ordered by a customer; request id, request type and request
content information is stored.
I asked about the composite key address and I got 2 possible choices right now: Create a table for address or create city, state and zipcode keys and add a constraint named address. However, it says that a domestic customer may have more than one address information. I don't know how to do that.
I Need to Design a database for a system where there's Customers and Vendors but they both are related to entity called Users where every user is either a customer or a vendor .
the problem is that Vendors are related to other entities that Customers aren't .
so how can I design such a database ?
The other entities will store the ID of the Vendor as a foreign key. And Vendors and Customers are not going to be in the same table anyway*, so it's not like the two have IDs that might be used at the same time for that.
Also, to add, the Foreign Key you require for User could be managed as an add/edit trigger if your DB of choice allows it. That way you can make sure that the Vendor id used for those related entities isn't a User ID linked to Customers. (...WHERE userid NOT IN (SELECT userid FROM users WHERE customer = TRUE))
* Customers and Vendors have different properties/fields so shouldn't be in the same table.
You could have Vendors and Customers have a relationship to a User table.
user
===========
userId
name
vendor
===========
vendorId
companyName
userId
customer
===========
customerId
source
userId
Then you can link to both customers and vendors from the same table, yet they can still share the same common data in the user table. In fact, a customer could also be a vendor.
Your question could be generalized as follows: how do I express subclasses in relational tables?
For the generic answer, see this:
https://stackoverflow.com/tags/class-table-inheritance/info
I am having a brain-cease on a data problem that I am in need of modeling. I will do my best to outline the tables, and relationships
users (basic user information name/etc)
users.id
hospitals (basic information about hospital name/etc)
hospitals.id
pages
pages.id
user_id (page can be affiliated with a user)
hospital_id (page can be affiliated with a hospital)
Here is where the new data begins, and I am having an issue
groups (name of a group of pages)
groups.id
groups_pages (linking table)
group_id
page_id
Now here is the tricky part .. a group can be 'owned' by either a user or hospital, but those pages arent necessarily affiliated with that user/hospital .. In addition, there is another type of entity (company) that can 'own' the group
When displaying the group, I will need to know of what type (user / hospital / company) the group is and be able to get the correct affiliated data (name, address, etc)
Im drawing a blank on how to link groups to its respective owner, knowing that its respective owner can be different.
Party is a generic term for person or organization.
Keep all common fields (phone no, address..) in the Party table.
Person and Hospital should have only specific fields for the sub-type.
If the company has different set of columns from Hospital simply add it as another subtype.
If Hospital and company have same columns, rename the Hospital to more generic Organization
PartyType is the discriminator {P,H}
You'd have to use some form of discriminator. Like adding a column with "owner_type", you could then use either an enum, a vchar, or just an int to represent what type of owner the column represents.
Here is a good tutorial on how to model inheritance in a database while maintaining a reasonable normal form and referential integrity.
Condensed version for you: Create another table, owners, and let it keep a minimal set of attributes (what users and hospitals have in common, maybe a full name, address, and of course an id). Users and hospitals will have their respective id columns that will simultaneously be their primary keys and also foreign keys referencing users.id. Give users the attributes that hospital's don't have and vice versa. Now each hospital is represented by two easily joined rows, one from owners and one from hospitals.
This allows you to reference users.id from groups.owner_id.
(There is also a simpler alternative where you create just one table for users and hospitals and put NULLs to all columns that do not apply to a particular row, but that quickly gets unwieldy.)
HospitalGroups(HospitalID, GroupID)
UserGroups(UserID, GroupID)
CompanyGroups(CompanyID, GroupID)
Groups(GroupID,....)
GroupPages(GroupID, PageID)
Pages(PageID, ...)
Would be the classic way.
The discriminator idea mentioned by #Robert would also work, but you lose referential integrity, so you need more code instead of more tables.
I have a problem with a many-to-many relation in my tables, which is between an employee and instructor who work in a training centre. I cannot find the link between them, and I don't know how to get it. The employee fields are:
employee no.
employee name
company name
department job title
business area
mobile number
ext
ranking
The Instructors fields are
instructor name
institute
mobile number
email address
fees
in a many-to-many relationship the relationships will be in a 3rd table, something like
table EmployeeInstructor
EmployeeID
InstructorID
to find all the employees for a specific instructor, you'd use a join against all three tables.
Or more likely there will be classes involved --
Employee takes Class
Instructor teaches Class
so you'll have and EmployeeClass table,
an InstructorClass table,
and join through them. And Class needs to be unique, or else you'll need
Class is taught in Quarter on ClassSchedule
and end up joining EmplyeeClassSchedule to InstructorClassSchedule.
This ends up being one of your more interesting relational designs pretty quickly. If you google for "Terry Halpin" and "Object Role Modeling", this is used as an illustrative situation in the tutorial.
First of all, you will need a unique key in both tables. The employee number may work for the employee table, but you will need another for the instructor table. Personally, I tend to use auto incrementing identity fields called ID in my tables. This is the primary key.
Second, create a new table, InstructorEmployee. This table has two columns, InstructorID and EmployeeID. Both fields should be indexed. Now you can create an association between any Employee and any Instructor by creating a record which contains the two IDs.