I am trying to put together a database that holds the relation between computers and orders where a computer can exist on many orders and an order can show many computers.
I have the structure so that there is an extra relational table showing the computers_orders_relationship.
My table shows, for example, computer_id, order_id, location_id, comments, etc that are specific to the computer for the specific order.
I'm confused whether I should add specific information about the specific order for that specific computer in the computers_orders_relationship table... any pointers?
Yes specific information about the specific order for that specific computer should be in that junction table.
It is an option, however, to add an auto-number field to the junction table and have this linked to another table that contains all these specific details. This can be more efficient if there a lot of details, and easier to maintain.
Related
I am building a database for my application using Mysql, contains 2 tables in which one table will have user details and other table will have all user's activities(say posts,comments,..). I have 2 approaches for this PS.
Group all users activities under one table(say useractivities).
Maintain specific activities table for each user(say user1activity,user2activity,...).
If we go with approach 1, it builds time complexity in case of more users.
with approach 2, eats up database. which design will show less time and space complexity?
For better database maintain, you have to go with the first approach because you can normalize data easily.. and the perfect way to manage database structure, Need to take care of below points
You have to give proper indexing in user_id field for fast result in join query.
In case of large number of records in one table, then you can create another table like user_activities_archive for store old activities. in the regular period, you can move an old record from user_activities to user_activities_archive
You can create multiple tables for user_posts, user_comments instead of user_Activities for more splitting data and different structures of the table, for example you can manage replyto_id in the comment table and user_post table might have title field.
In the second approach for cerate tables for each user, there are many limitations like
Very hard in case of Table Joining with other tables
In case of fetch all user's activity records, you cant do it.
A number of the user base of your application.
Limitation of a number of tables in the database.
Create more complexity in edit update or delete user records.
If the user is not active (just registered) then separate user table useless.
As juergen d mentioned in the comment, approach 2 should not be used.
However I would consider splitting useractivities into different tables if the possible user activites are different from each other to avoid unneccessary column.
Example: A comment table with information about who made the comment (foreign key to user table) and the comment itself. + A foreign key to another user activity to wich the comment was made.
The comment column in the above table does not make sence for say, just a like of a post, so I would have created a different table for likes.
I am in the process of designing a MySQL schema for a website which allows the visitors first to view the list of products (browsing or searching) and view each product in details. Only certain fields are displayed in the listing view and a lot more information is to be displayed when viewing the details, with some fairly big column data (e.g, the product description). The design is quite common. I am wondering what is a good way to store the product information.
One choice is just to have one PRODUCT table. Viewing the list will have a select a subset of the fields, say, name, price and the main product picture, but not including other fields like description which could be fairly big, say, a VARCHAR(2000). My question is that I do a select name, price, main_pic from product where ..., will the description fields also get loaded into the memory by MySQL engine, thus consume more spaces?
If MySQL does load other unselected fields into memory or simply just want to keep details in another table, there could be a PRODUCT_DETAIL table. Would this be a good design? I feel a little weird since both PRODUCT and PRODUCT_DETAIL would then have the same primary key, and because of the master-detail relationship between the two, the primary key of the PRODUCT_DETAIL would also be a foreign key referencing the primary key of PRODUCT! Anyone actually use this kind of design?
This question is similar and can help you.
Question : select * vs select column
And yes Master-detail type relationships are also used and is a good way to design.
I am running an e-commerce site with multiple stores and each store having its products. I currently have a table called product-store which has a list of all product id referencing the products name and description from a different table , prices etc and their corresponding store ids. This table could have same product repeating multiple times if multiple store carry it.
I am mooting the idea of having a separate table for each store(product-store1, product-store2) rather than having all stores in one product-store table. I could be adding 100 stores and hence 100 tables like this. The structure of each table is the same but the reason why I am thinking of doing this is for better encapsulation of data from the other stores. However this would also mean identifying the corresponding table first for the store and then fetching the data.
I need help in assessing if this is a right approach and how I can measure the two approaches.
There are very few good reasons for splitting a table into multiple tables. Here are reasons not to do it:
SQL is optimized for large tables, but not for lots of small tables with the same structure. (With small tables, you end up with lots of partially filled data pages.)
Maintenance is a nightmare. Adding a column, changing a data type, and so on has to be repeated many times.
A simple query such as "How many stores sell a single product?" are problematic.
You cannot have a foreign key relationship into this table, for instance, to have a history of prices or discounts on the product in each store.
A single table is almost always the best way to go.
I guess it also depends on if the products might be shared across different stores. I would not go the way of creating x tables for x stores, but a general structure to be able to hold all the information.
If so, you could set up at least three tables:
product (holds all the generic products information, shop independent)
store (information about the stores)
store_product (links the products to the stores)
This way you can add as many products / stores to your system without having to change database structure (which is bad anyways).
To answer some of your assumptions:
Encapsulation of data from different stores is rather selecting a subset of data that choosing different tables.
whenever you need some additional information (not being thought of in the beginning) for either stores or products, its easier to add by referencing the new table to stores/products instead of having to multiply those changes by the amount of stores.
i wanna have a Users details stored in the database.. with columns like firstname, last name, username, password, email, cellphone number, activation codes, gender, birthday, occupation, and a few other more. is it good to store all of these on the same table or should i split it between two users and profile ?
If those are attributes of a User (and they are 1-1) then they belong in the user table.
You would only normally split if there were many columns; then you might create another table in a 1-1 mapping.
Another table is obviously required if there are many profile rows per user.
One table should be good enough.
Two tables or more generally vertical portioning comes in when you want to scale out. So you split your tables in multiple tables where usually the partiotioning criteria is the usage i.e., the most common attributes which are used together are housed in one table and others in another table.
One table should be okay. I'd be storing a hash in the password column.
I suggest you read this article on Wikipedia. about database normalization.
It describes the different possibilities and the pros and cons of each. It really depends on what else you want to store and the relationship between the user and its properties.
Ideally one table should be used. If the number of columns becomes harder to manage only then you should move them to another table. In that case, ideally, the two tables should have a one-one relationship which you can easily establish by setting the foreign key in the related table as the primary key:
User
-------------------------------
UserID INT NOT NULL PRIMARY KEY
UserProfile
-------------------------------------------------------
UserID INT NOT NULL PRIMARY KEY REFERENCES User(UserID)
Depend on what kind of application it is, it might be different.
for an enterprise application that my users are the employees as well, I would suggest two tables.
tbl_UserPersonallInformation
(contains the personal information
like name, address, email,...)
tbl_UserSystemInformation (contains
other information like ( Title,
JoinedTheCompanyOn,
LeftTheCompanyOn)
In systems such as "Document Managements" , "Project Information Managements",... this might be necessary.
for example in a company the employees might leave and rejoin after few years and even they will have different job title. The employee had have some activities and records with his old title and he will have some more with the new one. So it should be recorded in the system that with which title (authority) he had done some stuff.
The best way to describe this scenario is to use an example. Consider Netflix: do they
store their orders (DVD's they mail out) in a separate table from their member lists (NOT members table, but a joiner table of members and movies--a list of movies each member has created), or are orders distinguished by using additional information in the same row of the same table?
For those not familiar with Netflix, imagine a service that lets you create a wish list of movies. This wish list is subsequently sent to you incrementally, say two movies at a time.
I would like to implement a similar idea using a MySQL database, but I am unsure whether to create two tables (one for orders and one for lists) and dynamically move items from the lists table to the orders table (this process should be semi-automatic based on the member returning an item, where before a new one is sent out, a table with some controls will be checked to see if the user is still eligible/has not gone over his monthly limit)...
Thoughts and pros and cons would be fantastic!
EDIT: my current architecture is: member, items, members_items, what I am asking is if to store orders in the same table as members_items or create a separate table.
Moving things from one database table to another to change its status is simply bad practice. In a RDBMS, you relate rows from one table to other rows in other tables using primary and foreign key constraints.
As for your example, I see about four tables just to get started. Comparing this to Netflix, the grand-daddy of movie renting, is a far-cry from reality. Just keep that in mind.
A User table to house your members.
A Movie table that knows about all of the available movies.
A Wishlist or Queue table that has a one-to-many relationship between a User and Movies.
An Order or Rental table that maps users to the movies that are currently at home.
Statuses of the movies in the Movie table could be in yet another table where you relate a User to a Movie to a MovieStatus or something, which brings your table count to 6. To really lay this out and design it properly you may end up with even more, but hopefully this sort of gives you an idea of where to begin.
EDIT: Saw your update on exactly what you're looking for. I thought you were designing from scratch. The simple answer to your question is: have two tables. Wishlists (or member_items as you have them) and Orders (member_orders?) are fundamentally different so keeping them separated is my suggestion.
A problem with storing orders in the members table is that there's a variable number (0, 1, or several) of orders per member. The way to do this using a relational database is to have two separate tables.
I feel like they would store their movies as follows (simplified of course):
tables:
Titles
Members
Order
Order_Has_Titles
This way an order which has a foreign key to the Members would then have a pivot table as many orders could have many titles apart of them.
When you have a many to many realtionship in the database you then need to create a pivot table:
Order_Has_Titles:
ID (auto-inc)
Order_FkId (int 11)
Title_FkId (int 11)
This way you're able to put multiple movies apart of each order.
Of course this is simplified, and you would have many other components which would be apart of it, however at a basic level, you can see it here.