Category of database management systems characterised by the ability to join two data sets by matching on common fields, using mathematics-based relational logic.

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JOIN to read first table and get possible relationship in the second table

Consider a main table as CREATE TABLE groups ( group_id int(11) NOT NULL AUTO_INCREMENT, group_title varchar(255), PRIMARY KEY(group_id) ) ENGINE=InnoDB and a second table for relationship as ...
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1answer
112 views

How would I change this relational model to fit a nosql database?

Because of things beyond my control, I have to switch from a relational database to MongoDB for the advertising platform I'm helping to build. I've got a relational schema sketched out, but I'm unsure ...
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1k views

Candidate key = Key = Minimal Superkey?

I got a little confused by all these keys. As I understand A key of a relational schema = The minimal subset of a superkey that is still a key = A candidate key Is this correct or not?
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87 views

Index optimization

I'm building a 'tag' system for my blog posts. Currently my tags table has columns tagid - MEDIUMINT NOT NULL AUTO_INCREMENT PRIMARY KEY and tag VARCHAR(30) NOT NULL UNIQUE. And I have another table ...
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174 views

Separating tables vs having one table

At the moment I have a table setup that looks somewhat like this: create table tbl_locationcollections ( id int(11) PRIMARY KEY IDENTITY, --(Primary Key), name varchar(100) not null, ...
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157 views

Is it better to use multiple one-to-many relationships, or polymorphic?

I've got the following tables: Clicks table Websites table Ads table Both Ads and Websites have many Clicks (i.e. both models have a one-to-many relation with Clicks). In such cases, is it better ...
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1answer
242 views

Switching to NoSQL for native JSON use?

I am rather comfortable writing concrete schemas with explicit primary keys, foreign keys, indexes, views and stored procedures. For queuing I use a NoSQL solution called: Redis. Recently I heard a ...
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228 views

Use cases for NoSQL databases: Time series

I need to set up a database that will record temporal series data (sensors). A friend of mine has recommended me to use a NoSQL database instead of using Oracle (for instance). There're also some ...
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1answer
315 views

Delete entry from related tables

I can not use InnoDB engine because of some dependency troubles in LuaSQL and PtokaX. My current query is something like: DELETE e.*, m.* FROM entries e INNER JOIN magnets m ON m.eid = ...
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1answer
200 views

Foreign Keys with Composite Key

Imagine I have a table with the following dependency: (Name, BoughtFrom, TimeBought) --> Cost Where the three attributes in bold form a composite primary key for the table. Now then, I want to ...
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2answers
268 views

MySQL - Normalization over meaningless data - Compound Primay Keys or Surrogate ID field

Please forgive my title; if you have a suggestion for it, feel free to comment. I have a database: DROP TABLE IF EXISTS `books`; CREATE TABLE `books` ( `isbn` VARCHAR(255) NOT NULL, `title` ...
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1answer
366 views

Record with variable number of columns?

I am trying to model a cable mapping for devices. Each device has multiple cards, and each of those cards has multiple ports. Since both the number of cards and ports vary, I am confused on how to ...
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1answer
842 views

Modeling a ticket system based on a set of disparate kinds of tickets?

I'm working on a project that allows for the creation of "support tickets." These are not confined to something that needs fixing, however, so in a way they could more accurately be called "jobs." ...
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1answer
144 views

What is the real-world purpose of an optional 1:1 relationship?

I know that one-to-one relationships can be used to split data into multiple tables for performance or security and that it is used to create a is-a-relationsship. But aside from that things, what is ...
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2answers
452 views

Best relational database structure for this data

I'm in the process of creating a database scheme for the following scenario: There are users Users have roles (such as "Developer" or "CEO") Roles have applications (such as "Topdesk") Applications ...
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3answers
775 views

Database Design Relationship for Patient Visit in MS Access

I am designing a database to store records for research purposes, and I am having trouble picturing how I can create a relational database based on the information I have. There are a total of 6 ...
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4answers
285 views

Arbitrarily ordering records in a table

A common need when using a database is to access records in order. For example, if I have a blog, I want to be able to reorder my blog posts in arbitrary order. These entries often have lots of ...
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0answers
55 views

Create Scheme that allows for fluidity between entities [closed]

We are a small rapidly evolving company and recently investigated switching databases from SQL Server to a graph database. We like the graph approach because of the fluidity and openness that it ...
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1answer
233 views

Database Relational Design for Multiple Categories

I am building a database for participants who are grouped into studies. There's a total of 5 different studies - A, B, C, D, and E. The participants may be in more than one studies, and participants ...
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1answer
56 views

Correct data model for users with clients

I have an application where users are granted access. Part of the system allows users to have their own 'clients'. I have a users table ******************************** users ...
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3answers
4k views

How to have a one-to-many relationship with a privileged child?

I want to have a one-to-many relationship in which for each parent, one or zero of the children is marked as a “favorite.” However, not every parent will have a child. (Think of the parents as ...
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1answer
92 views

Looking for a scalable relational database [closed]

I'm looking for a database that achieves the following: fully ACID. relational with joins. has transactions. allows the administrator to specify sharding rules (for example: users from Europe should ...
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2answers
385 views

Relationships in a school database

I am designing database for a school app. Student is the main entity in the database. Student has relation with Parent & Guardian. I am confused as where to store references. As will student ...
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1answer
544 views

SQL Server 2008 - How would I create a dynamic query for finding relationships and references to the primary key?

Since I'm new and I've never shared, and yet there are a few useful scripts that I need on a daily basis, I thought I should. As a new DBA, some data fix DML operations and simple business logical ...
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1answer
138 views

Optimised Schema for City-to-City Distance Table

This is my first question, forgive me if this question is simple. I'm stuck here, trying to implement the relations for the data represented below. I want to scale it vertically (new rows), instead of ...
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1answer
112 views

Relation candidate keys

I have the following relation: R = ABCDE F: AB->DE, AC->B, DE->C, AE->C, C->AB I need to determine this relations candidate keys. Now, if I understood the defintion correctly: ...
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212 views

How should I model a worflow of status/activities ? (rules like “if is 3 go to 4, if is 4 go to 5” etc)

I'm trying to model a workflow (status and activities) to create "rules". Let me give you an example. The main "object" let's say are "vehicle requirements", I will have this table: idRequirement, ...
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1answer
107 views

Can I place the attribute in the Entity, when the foreign key is also already present?

I am using DBdesigner Fork for generating ER diagram. I have the 'Company' as an entity for which can I place the attribute of 'idShares', despite of having the foreign key of Shares Entity in the ...
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2answers
1k views

Database Design - One table for different types of transactions

Considering a procurement system as an example. Would it make sense to have one single table for the following: Quote, Order, Invoice and Credit Memo? There will be some details that are different. ...
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2answers
66 views

View for a MANY_MANY_MANY relationship

Let's say I have 3 main tables: category, tag, url category and tag have a MANY_MANY relationship (category_tag). tag and url have a MANY_MANY relationship (url_tag). I would like for a given ...
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2answers
99 views

Table Design - Identical tables for different statuses

I am developing a transactional System and the below is a simplified scenario of my problem. Users enter JOBS in a system. A User first enters a JOBS with a DRAFT status (and the Job is given a ...
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1answer
1k views

How to model entities in an entity relationship diagram?

I'm a beginner Database designer and wondering if anyone can help me understand this. Let's say we want to design a system that has, among other entities, an entity called Vehicle, and another one ...
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1answer
472 views

Applying user-defined fields to arbitrary entities

Currently we have an old (rather crude) system that has user-defined fields, which are mapped against rows in arbitrary tables. This was an after-the-fact modification based on a customer request, and ...
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0answers
130 views

SQL relationships, one-to-one, many-to-many etc [closed]

I'm trying to understand all relationship types that can be created in SQL. So far I only get the "belongs-to" one - Example: a table with "Blog post" records, which contains an author_id column that ...
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3answers
990 views

First Normal Form, why is it good and how does it reduce redundancy

I asked a similar question on SO and was advised to ask the type of question here. This is for a course on relational databases. A sample problem asks "how come every table in a relational database ...
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2answers
6k views

MySQL Workbench, how to refresh EER diagram?

I'm using MySQL Workbench to design my MySQL database and model how entities would look like and how they would relate to each other. Now, sometimes I use Doctrine ORM. When using Doctrine ORM, I ...
2
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0answers
2k views

Schema for an RBAC (Role-based Access Control System)

I want to implement an RBAC, Flat based. I've decided to base my system on the NIST standardization model. Although all fine and well, I have an inclusion to that design. Instead of a hierarchy ...
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1answer
636 views

Friends relations in MySQL

I'm developing a friendship relation in MySQL where friend relation is mutual. If A is friend of B, then B is friend of A. If one of the users end friendship then relation drops. I want to learn which ...
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1answer
1k views

How do I persist recurring events?

I've been tasked with designing a system to recur events. Events may recur daily, hourly, monthly or yearly. Users should be able to schedule events "every 3rd Wednesday of the month" or "The 1st of ...
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2answers
3k views

Designing a user authenication (Roles & Rights) module

I am trying to model a User Authentication module for a MS SQL Server database that will be the back end to a Delphi UI Application. Basically, I want to have user accounts where the user belongs to ...
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2answers
144 views

Which tables to create according to relations

We are planning a new system with a new DB (MS SQL Server). We have the following entities and the following relations: Entities: Clubs, Chains, PaymentTypes, etc... Relations: Clubs-Chains (M-M); ...
4
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1answer
126 views

unique constraint on a set

With reference to this SO question, what would be a correct way to implement Unique tag Combination Constraint in SQL Server 2005? To illustrate the problem, I make an example: A tag_bundle consists ...
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1answer
417 views

What is the correct way to store a list and its items in this instance?

The app I'm working on revolves around projects. Each project can contain several lists, and each list is made up of several items. Each list relates to a single project. Is it better to have one ...
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1answer
44 views

What is this type of query called, and how can I formulate it?

I have following tables: events(event_id, name, description) groups(group_id, event_id, title, description) event_group(event_id, group_id) users(user_id, name, email) ...
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1answer
137 views

How can I improve this design?

I'm creating an event planning PHP/MySQL web application as a learning project. The whole app revolves around the idea of the event and its various components (participants, groups, lists, etc.) I ...
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1answer
544 views

How to use a relational database to store all users who belong to a group, and all groups which a user belongs to?

This is a beginner question: A user can belong to many groups, and a group can contain many users. Let's say the two tables look something like this: user_id user_name user_email group_id ...
2
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2answers
207 views

mySQL Relational Tables

Say I have 3 tables Products, Orders and Orders Product Products Table ID | StockNum | Description | Price 4 | 452SB | Black | 45.65 5 | 752SA | Green | 17.12 Orders Table ID ...
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309 views

Database structure, relational or data warehouse?

Good morning, Im having some issues with how my database should be laid out and would appreciate some guidance. I have several tables (rainfall data), each containing the following columns: Date ...
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4answers
357 views

Database Design for updatable sequential records

I am working on creating a data model for storing data related to production tracking. I work for an engineering firm that models and analyzes data for our clients. There are several steps in the ...
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1answer
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Difference in between HAS MANY and BELONGS TO in Yii framework [closed]

I am new to the Yii Framework. I discovered HAS MANY and BELONGS TO in the documentation, however I am confused about these features. Can someone give some real life examples with a diagram that ...