Good evening,
I currently have 3 tables on my API at backendless.
**Users** (objectId, email, username, password)
**figures** (objectId, figure_name, figure_cat, figure_image, figure_info)
My figures data has rows kind of like a product.
Basically, I would like to link entries in the figures table to users but i'm not sure the best way to go about it.
I can create relationships of one-to-one and one-to-many but being new to that i'm not sure the best way to go about it.
Any help or advice would be much appreciated :)
does a user have many figures?
Can multiple users share the same Figure?
Assuming that a user has many figures, so you will have a userid column in the figures table (1:M rel between user->figures). I also assume your figure_cat is a relatively static list, so consider a lookup table for that so it has a fkey in the figures table as well. Also depending on the size of images, it may be better to put images in a different table so you can put them in a different file group.
Assuming figures are shared by users, you may need a M:N table in between users and figures that stores the userid, to figureid mapping (sometimes called a "tie table" I think)
What database are you using?
You can create a relationship between the tables either directly in the console or by making an API call where you save an object which references other (related) objects. See the documentation for details: http://backendless.com/documentation/data/js/data_relations.htm
Related
I have an interesting situation where I'm working with posts. I don't know how the user will want to structure the posts. It would either be one block of text, or structured in an a-> b -> c structure where a, b, and c are all text blocks, and if represented as a table, there would be an unknown number of columns and unknown number of rows.
Outside of the post data, there is the possibility of adding custom attributes to the post. Most of these would be shorter text strings, but an unknown number of them.
Understanding that a json object would probably be the simplest solution, I have to fit this into a self-serving db. SQLite seems to be the current accepted solution for Redwoodjs, the framework I'm building out of. How would I go about storing this kind of data within Redwoodjs using the prisma.js that it comes with?
Edit: The text blocks need to be separate when displaying the post and able to be referenced separately. There is another part of the project that will link to each text block specifically. The user would be choosing how many columns there are before entering any posts (configured in settings), but the rows would have to be updated dynamically. Closest example I can think of is like a test management software where you have precondition, execution steps, and expected results across the top for columns, and each additional step is a row.
Well, there are two routes that you could take. If possible use a NoSQL database, such as mongoDB, which Prisma has support for. There you would be able to create a JSON like structure with as many or as little paragraphs you would like.
If that is not possible a workaround, since SQLite does not support JSON data, you could store the stringified JSON data in a text field, and then parse it. This is not the optimal solution, so if possible use the first one.
I'm acutually trying to make a one-to-many relationship between the auto generated table "jhi_user_authority" and my own table called socialMediaFilter.
My situation is the following:
On the one side I have users, these are saved in the table "jhi_user" these users have roles and the roles for themselves are saved in a table called "jhi_authority". Between users and roles is a many-to-many relation, that means that many users can have many roles. These relationships are saved in a join-table called "jhi_user_authority". All these 3 tables are auto-generated by Jhipster when I created the project.
In my project I need to add some filters for filtering data from social media networks, twitter, fb and so on. A filter belongs to a role and a role can have many filters. So between these two tables is a one-to-many relationship and I'm struggling implementing this in my project.
I cannot access these auto-generated tables with the jhipster:entity generator. When I'm using for example yo jhipster:entity authority jhipster tries to generate a new entity. And as far as I know - these auto-generated tables are not meant to be accessed by the entity-generator. So when I want to edit them I need to edit them manually, so I can not follow the instructions in the tutorial.
Is there maybe someone who can pushes me to right direction? :D
thanks,
Alex
EDIT:
okay...after thinking for a while i figured out that i need to do it different
the relationships i need to implement should be like this uml
but i still have problems realizing it
Good morning, you have to do an n-m relation with the "Authority" class, in which you must specify that the relationship table is "jhi_user_authority"
well, i am creating a network that allows users creating posts and like them.
Asking on stackoverflow i've understood how to structure my database:
A collection which includes a document for each post.
A collection which includes a document for each like, in each of these documents there is a reference to post is referenced to.
When i want to get ALL likes about a post i can query the like collection looking for the reference to that post.
And till here i am ok. But assuming i'll have millions documents in like collection, i wondered how could i query and search among them in not too long time.
And i was advised of ensureIndex, in this case, i have to ensureindex of the field which contains reference to a post.
But when do i have to create this index? is enough to create it once (for example when i set up my database) and it will be as default in mongodb or do i have to do it during application life-time? thank you
But assuming i'll have millions documents in like collection, i wondered how could i query and search among them in not too long time.
I assume you would most likely want to do a count on the likes as an example?
You can't, instead you use optimizations to combat this. A count on millions of rows might get a bit slow.
A typical scenario are counters in SQL techs that you use to amend the parent row with a sum figure of its children.
Same applies to MongoDB.
You would aggregate important data to the top.
If you require to actually query the likes to show some who have liked it then you limit those likes. Google+ and other networks tend to limit the amount of likes they show to about 1,000.
And i was advised of ensureIndex,
Adding indexes to a database does help with actually searching for documents.
But when do i have to create this index? is enough to create it once
Yes, MongoDB will manage the index itself. You only need to ensure it once.
I am creating a mock app with user creation/auth/friend in a node js learning exercise. Having spent my time mostly at the front end of things, I am a n00b as far as DBs are concerned. I want to create a user database where I want to keep track of user profiles and their connections/friends.
Primary objective is to load/store users connections in the database.
Fetch this information and give it to the user most efficiently in least number of queries.
I'd really appreciate some help with a DB structure I should be using that can accomplish this. I am using mongodb and node.
Off the top of my head: I can store the user's connections in an object in the "connections" field. But this will involve making a lot of queries to fetch connections' details like their "about me" information - which I can also store in the same object as well.
Confused. Would really appreciate some pointers.
Take a look at the Mongoose ORM. It has a populate method that grabs foreign documents. Lots of other great stuff too.
You could say
Users.find({}).populate('connections').exec(function(err,users) { ... });
Before popualte the users' array of connections was an array of IDs, after, its an array of user documents.
This is something that has intrigued me a lot recently. It's a general SQL/Relational Database problem coming from a guy who prefers Mongo.
What I want is, to, as such, associate data from different tables in the most efficient, easiest way, without using associations and assuming I can't restructure or re-model the db.
So, for example, with FQL (which doesn't have associations), if I asked for the name and eid of all the events my current user has been invited to, I'd also like to know whether my current user is going, but that info is in the 'event_member' table.
In this instance I've an interest in another column (rsvp_status) in event_member, one that I'd like to be associated with the columns from event, i.e eid and name.
In this case the instinct may be to say that since every event has a name, an eid and a rsvp_status then we could say sort by eid and then match each nth item (for n=1 to whatever), because there's guaranteed to be the same number, but there are many cases when we can't do that.
And I know I could do separate queries and then iterate through and match them by eid, but basically I'm looking for a generic, simple,efficient solution for the associations idea if one exists. Preferably in javascript.
What you are looking for here is a simple JOIN of two or more tables. http://www.w3schools.com/sql/sql_join.asp
You do not have to have any relations between tables in order to perform JOINS. The relations are just a constraint to ensure that bad/invalid data can't propagete to the tables. For example an event_member with eid of unexisting user. Anyway you are free to JOIN tables as you like :)
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