Am wondering if anyone might provide some conceptual advice on an efficient way to build a data model to accomplish the simple system described below. Am somewhat new to thinking in a non-relational manner and want to try avoiding any obvious pitfalls. It's my understanding that a basic principal is that "storage is cheap, don't worry ...
Hi This is my first question in this forum, so please bear with me and I hope I'm not violating any rules. I am looking at different ways to model scattered 3d data as a gridded function (over xy support, z=z(x,y)). Answering another question, coryan was so nice as to mention the method using heat equation to interpolate (approximate) a...
What is the best way to document a logical or conceptual data model. Whilst tools like Visio allow you to define entities, attributes and relationships they do not support the collection of other vital information about a model such as validation rules, entity life cycles data owners. They also aren't very useful for communicating the...
At linkedin, when you visit someones profile you can see how you are connected to them. I believe that linkedin shows upto 3rd level connections if not more, something like shabda -> Foo user, bar user, baz user -> Joel's connection -> Joel How can I represent this in the database. If I model as, User Id PK Name Char Connecti...
Hi all, When you are developing an MVC based website that will, for instance, be able to display profile information about a user, how do you usually model data if it's coming from a relational database so that it would still be useful if the persistent storage mechanism changes (perhaps to some SOAP or XML based webservice)? For examp...
I'm doing a schoolwork and.. I have to do a vehicle tracker system. I thought of these three designs. What do you think? My database schemas (png at ImageShack ~99KB) http://img390.imageshack.us/img390/3781/des.png Opinions? ...
My Schema looks like this: CREATE TABLE items ( id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, description TEXT NOT NULL, quantity INTEGER NOT NULL price TEXT NOT NULL, category_id INTEGER NOT NULL ); CREATE INDEX "item_id" ON "items" ("id"); I'm setting price as TEXT but it probably should ...
I'd like to improve my understanding of cardinality constraints in ER diagrams. I have two entities: User Location But, I want the relationship between these two entities to be many-to-many (a user can be in many locations and a location can have many users). To do this I need to introduce an association class UserLocation. Is it ...
I'm completely new to Mongo and RoR, coming from a PHP background. I was just going through this tutorial about data modelling http://www.mongodb.org/display/DOCS/MongoDB+Data+Modeling+and+Rails and was struck with the question of why the tutorial would recommend storing the votes in a field and updating that field as db.stories.upda...
Dear all I am looking at writing an application that handles time series data and want to shove to heavy lifting data work off into Core Data. My question is this - from a speed of retrieving and ease of manipulation perspective, would it be better to model out the entities or will it likely be easier to 'store' the time series data po...
This is a particular problem that I have come across many times, but I have never really found a simple solution to this (seemingly) simple problem. How to you ensure that a given parent has a fixed number of children? 1) Example. How do you make sure a given class has only , say, 50 students enrolled..? create table class( class_...
Let's say that in a project your entire domain can be modelled with a single root say "Company". So is it logical then to say that my DAL exposes only 2 methods :- save and delete to the business layer and all other things are done at business layer ?? or is it bad design ?? Context : I am new to ORM and am currently involved in a projec...
If I were to have an online shopping website that sold apples and monitors and these were stored in different tables because the distinguishing property of apples is colour and that of monitors is resolution how would I add these both to an invoice table whilst still retaining referential integrity and not unioning these tables? ...