Hi, I'm trying to make a SELECT on three relational tables like these ones: table_materials -> material_id - material_name table_props -> prop_id - prop_name table_materials_props - row_id -> material_id -> prop_id - prop_value On my page, I'd like to get a result like this one but i have some problem with the query: material pr...
Hi. I created a function in C# which allows me to copy a record and its related children to a new record and new related children in the same database. (This is for an application that allows the use of previous work as a template for new work.) Anyway, it works great... Here's a description of how it accomplishes the copy: It popul...
How would i get the last 20 results submitted in a mysql db row. I need the 20 most recent user submitted results. Cheers. ...
If you had a webshop solution based on SQL Server relational DB what would be the reasons, if any, to move to NoSQL storage ? Does it even make sense to migrate datastores that rely on relations heavily to NoSQL? If starting from scratch, would you choose NoSQL solution over relational one for a webshop project, which will, after a while...
Content of a website is stored in a MySQL database. 99% of the content will be enabled, but some (users, posts etc.) will be disabled. Most of the queries end as WHERE (...) AND enabled Is it a good idea to create an index on the field 'enabled'? ...
Hi, Is there any software/tool which can be used to generate DDL(Data Definition Language) from the ER Modal diagram ? Currently I am using Microsoft's Visio Architect to generate DDL from a VSD file. I want an open source or free software which can serve the same purpose. ...
Hi I have the following relations (tables) in a relational model Person person_id, first_name, last_name, address Student person_id, matr_nr Teacher person_id, salary Lecture lecture_id, lect_name, lect_description Attendees lecture_id, person_id, date I'm wondering about the functional dependencies of Student and Teach...
I'm trying to set up a relational View but not sure how to do it. Here's an example of what I'm going for using the node types Artist and Song. Artist Song Length Bob Dylan Like a Rolling Stone 2:00 Bruce Springsteen Atlantic City 4:00 Burce Springsteen Born to Run ...
Hi , I've defined table with this schema : CREATE TABLE [dbo].[Codings]( [Id] [int] IDENTITY(1,1) NOT NULL, [ParentId] [int] NULL, [CodeId] [int] NOT NULL, [Title] [nvarchar](50) COLLATE Arabic_CI_AI NOT NULL, CONSTRAINT [PK_Codings] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON ...
Hi, to explain my problem, I'll give a simple example: My database has three tables: [positions] - position_id INT - position VARCHAR [employees] - employee_id INT - position_id INT - FK - name VARCHAR - birth_date DATE [vehicles] - vehicle_id INT - model VARCHAR - year VARCHAR - color VARCHAR The problem is that I must ...
Other than Linq, have their been any other attempts to integrate relational features into an object oriented language itself, rather than just the libraries? UPDATE On of the most obvious examples is one-to-one, one-to-many or many-to-many relations. Then you can also consider relationships having properties themselves. ...
I am new to rails, and have a situation that I can't quite get my head around. Lets say I have two resources, users and widgets. Users can use widgets, but widgets are also user created, and should be owned by the user that created them. There needs to be a user uses widget, and a user owns widget. Is the following what I am looking ...
Hi, I'm having the following problem with 2 MySQL tables that have a relation: I can easily query table 1 (address) when I want a full list or filter the result by name or email or such. But now I need to query table 1 and filter it based on the relational content of table 2 (interests). So, I need to find a row (usually many rows) in ta...
Hello, I'd like to design a JVM data structure (Java/Scala) that can be used to represent and store the contents of arbitrary relational database tables. The data structure should be fast (not too gc-intensive, cache-friendly) and memory efficient, so larger tables can fit in RAM. One memory-efficient solution is to store each column ...
Hopefully my description is a little better than the title, but basically I'm having an issue with one part of a new application schema and i'm stuck on what is the most manageable and elegant solution in table structure. Bare bones table structure with only relevant fields showing would be as follows: airline (id, name, ...) hot...
hi, maybe the rails pros here can help me with the software design of a contact management web app. i want to create Groups, where I can add Contacts to. I thought I generate a Group scaffold and a Contact scaffold with group:references Then I the models to Group: has_many :contacts Contact: belongs_to :group I also set the rou...
Say I have a table of apples (apple_id). And for each apple I have a history of its weight over time. How to structure it so that every time an apple is added, an associated table is created with its weight history? Having only one table of weight history for all apples (apple_id,age,weight) seems like a performance drain when looki...
what is the equivalent relational algebra operator for not exists (in sql)? That is how do i represent not exists in relational algebra ...
Hi everyone. I would appreciate any help with this. I have a simple container template class Dataset. Also there is a specialization to allow a different implementation when a Dataset of Datasets is instantiated. Since a Dataset of Datasets would be a heterogeneous container, there is a base abstract class List wich must declare a com...
i would like to check if my relational algebra statements are correct, so is there a program out there that outputs relational algebra equivalent of an SQL query? ...