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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compound primary key with separate id field for reference

I am trying to build locations into a database like so: Country -> Region -> Town Countries will be populated with a list of pre-defined worldwide countries, regions & towns are input by users. ...
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18 views

Storing generated documents that can not be updated by changes in relationships

I have a system running with PostgreSQL and Yii Framework, which generates a few medical documents that, once ready, can't be changed. For example: If my full name comes out on this document today, ...
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51 views

Spotting foreign key relations in a database that doesn't define all relationships as constraints?

At work I use a rather old MS Access database which defines some relations between tables, but does not outright define all of them. If the database application used an ORM, I would think that this ...
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225 views

When normalizing a relational database, should multiple “type” tables be combined into one?

Before making substantial changes to the content, functionality and design of my website (I'll be refactoring everything, almost a complete rewrite), I'm setting up a new PostgreSQL database to hold ...
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2answers
102 views

Algebra of joins, is there ever a need to repeat a table in a series of joins?

First, I'm just asking about inner joins. And, I'm thinking self joins or reflexive joins through a join table are special cases which depend on how the data is structured (e.g. city - state - ...
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1answer
95 views

Relational Model Design - Entity with one attribute

I am trying to desing a database relational model for an assignment. At first, I design the ER diagram and next the relational model with tables(Schemas). So here's my question : Is it possible for an ...
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1answer
172 views

Airport Database Design guidance required

I am trying to make a generic database for airport management and DBMS would be oracle 11g xe. Since, i am amateur and still learning so i have tried to kept the problem statement simple with limited ...
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1answer
64 views

Which one is correct and optimized in sql?

Imagine that I have three entities (EntityA, EntityB, EntityC) that can have some images. So there are two ways: Make an image table for each entity. It means that EntityA has a image table named ...
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587 views

Database design: Normalizing a “(many-to-many)-to-many” relationship

Short version I have to add a fixed number of additional properties to each pair in an existing many-to-many join. Skipping to the diagrams below, which of Options 1-4 is the best way, in terms of ...
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67 views

Create one-to-many to two fields in different table

I have a database where I am trying to figure out how to join a table that contains an object called ModelType. The calibration table contains two fields (EffModel and BkgModel) that are based on a ...
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1answer
91 views

Table with multiple lookups

I bet this may be a duplicate and I'm not forming the question correctly, so feel free to point me in the right direction. Background We have a SQL Server with some legacy data. They're all ...
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1answer
97 views

Attempting to identify transitive dependency

Hello I am attempting to identify a transitive dependency in the following diagram. I think that possibly the determinate of "Subtotal" is "Quantity" and "Price Charged" but I'm not sure if "subtotal" ...
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1answer
50 views

one to one relationship

This is my database structure: Users {user_id, username} Profiles {profile_id, user_id, user_views} My question is: If I do it the way mentioned above, should I to set user_id as primary key or ...
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1answer
134 views

Two relations to same table in SQL Server

I've got two tables. When I delete a row in Table1, I want to set the ID of that row in all the rows of Table2 to NULL. I've got two relationships on Table1. The problem is: I can only set one delete ...
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2answers
74 views

Oracle tables partition related

Here is my doubt. Is it possible to apply a partition to one table depending in the partitions values of another one? Why I am asking? I have one table where information headers are persisted, and ...
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2answers
97 views

What are the possible risks involved in partitioning large database tables? [closed]

There has been much talk about the benefits of table partitioning in Relational DBMS. I would like to know: Are there any risks to table partitioning ? What measures are there to take to minimize ...
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1answer
646 views

MySQL Workbench - Creating a one-to-one relationship using existing columns?

How do I create a one-to-one relationship using existing columns in MySQL Workbench? I have an EER diagram tab open and I am selecting from the toolbar on the left hand side. Unfortunately it seems ...
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1answer
79 views

What Happens when Cartesian Product is applied to Relations with same attribute name

I understand that the Cartesian product(X) operation on two databases does not need to be UNION compatible.So,if there is a same attribute called name in the two relations R and S where name in R is ...
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88 views

How to join the tables in mysql to get wall messages and comments with name of person ? Only user and his friends messages

I have four tables in my mysql database as shown in the image url provided. I want to select data from the tables without duplication. I want to show messages and comments on wall according to the ...
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1answer
27 views

Normal form for a relation where the number of tuples having the same value in a column is the same for all the possible values in that column

Is there a normal form for a relation that would permit the following table : id | alpha ---------- 1 | a 1 | b 1 | c 2 | g 2 | u 2 | k . . . n | x n | y n | z But not this table : id | ...
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1answer
67 views

Database Designing Issue

I have a database having Millions of records in three tables. Now i want to split these three tables in multiple tables to reduce redundancy and data duplication. A lot of records(Persons) have ...
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19 views

Junction table for peer entities and uniqueness for a link [duplicate]

In my database I have two tables: for peer entities (e.g. Persons) and for links between them (e.g. Friendship). Obviously, the latter table contains at least two references to the former table (e.g. ...
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1answer
551 views

tables for different sources of payments

Selling software products. I have a table "licences". Each software licences is created due to a payment. I am creating tables to accept payments from different sources (e.g. manual or PayPal.) I'm ...
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1answer
27 views

Effectively modelling extended classes

I have 3 different types of content for a website, 'Article', 'Video', 'Review'. Each of those three types of content contain common fields and type specific fields. For this, I have created the ...
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76 views

How to represent group by in relational algebra

I have to plan a plan tree based on relational algebra.My question is that at some point I have a SORT ORDER BY the output of a join, so how do you represent group by in relational algebra.
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60 views

Why NOSql should be more performant than RDBMS under structured data loads?

The main reason NoSQL dbms have become so common is the need of storing unstructured data where a Relational database instead would require carefully designing a database schema and fitting data into ...
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1answer
468 views

Relationships between subtypes of an entity

I have a very big (hundred of milions rows) table which represent an entity (event) having many subtypes (different kind of recorded events). Each row is identified by an id (obj_id) and has an ...
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2answers
130 views

Multiple relationships between the same entities

Is there a name for when 2 entities can have multiple relationships between them?
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1answer
58 views

is-a relation(ERM) to tables

i try to design a database with an is-a relation: Vehicles have some general attributes and the SubVehiclesX have some specialized Attributes. SubvehicleX is a Vehicle And a Person has a Vehicle ...
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2answers
187 views

How to establish a Two-to-One table relationship (PK-FK-CK)?

My question is about DB design and its principles. I am working on a Python application where objects are mapped to database tables. I have Projects and People objects, mapped to their respective ...
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2answers
126 views

Can relationships have relationships?

I have the following requirements (as part of a larger system). In the database, I need to maintain a list of parts, suppliers who sell those parts. Many suppliers can sell the same part and each ...
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79 views

Can XML columns in Oracle/MS SQL Server replace document oriented databases to some extent?

Just a strategic question: I am currently working with frequently changing data schemas and it takes a lot to keep track of versions and specific content. I do, however, have a classic OLTP ...
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506 views

Number of ISA relationship triangles in an Entity Relationship Diagram

The following two diagrams are nearly identical. However, in one, there are two ISA triangles from the Entity "Movie" and in the other there is just one. What is the difference in meaning?
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158 views

In mySQL possible to change auto-increment ids that have huge gaps and if so how?

I am importing a 50 table relational database (I'm not a dba) with 250,000+ records in most of the tables, yet the auto increment is off in most tables, some for example showing the last ID at 5 ...
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1answer
480 views

Advantages of middle tables in one-to-many relationships

Entities: Lists Leads What I am trying to achieve is a scenerio where in the relationship between lists and leads the following constraint is applied: A list can have many leads, but a lead can ...
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1answer
26 views

Good idea to include summary of frequently accessed data from another foreign-keyed table?

Sorry for poor title, I'll try to explain it in more detail here. I have an application that often gets a row from table A, then looks up a column from that in a foreign key mapping table (table B), ...
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110 views

Multiple relationships issue

Here is my SQLFiddle: http://sqlfiddle.com/#!2/affc4/9 A brief description of the issue: I have the following data: topics brands celebrities All 3 of those data types can be associated to an ...
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931 views

Diffrence between relational and unrelational database [closed]

What is the difference between relational(MySql) and unrelational database(MongoDb)
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89 views

Need advice on this EER Diagram

This db will work with a CakePhp app and need advice about design. Is it good idea to put orders on center or should I put clients on center? Clients has orders and an order record can only have one ...
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2answers
81 views

Several stays: many-to-many relationship

Could you please help me with the following problem? I'm a total novice in DB design. I have a table with researchers who visit our university. They come for some period of time (from, till). Now, ...
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64 views

Table Structure: 2 Related Entities Share the Same Entity

I was hoping I could get some advice on my table structure. Im writing a simple workout tracker for me and my buddies. These are the requirements: Multiple users A user can have multiple workouts A ...
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1answer
359 views

Event Management System

I'm working on a "Event Management System" Online Software Project where the system requires the following: Viewers can sign up for their user account Events can be created by the admin from the ...
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500 views

The nature of the relationship between two tables in MySQL

Good day. I'm designing a database for a research project where we're predicting whether or not young female athletes will rupture their ACL(s) based on the nature of a test jump recorded with a ...
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1answer
587 views

What does a round relationship icon mean in MySQL Workbench Visual Data Model

I have created a model in the Visual Data Model of MySQL Workbench, and on one single relationship, this icon shows up: What does it mean? The Relation is 1:1, and this icon shows only on this ...
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135 views

Is there any way to tell the number of matches found in a database value matched with LIKE?

Is there any way I can query a SQL-Server-CE database that will return the number of matches found in a cell value using LIKE (or MATCH AGAINST or any other method I'm not aware of, really)? EXAMPLE ...
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2answers
29 views

Help wrapping my mind around many-to-many relationships

I'm making a database that needs to have the following tables: Article, Video, Image, and Keyword. Keyword contains a fixed list of keywords. (For example when creating an article, you'd have to ...
2
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1answer
31 views

NEWB Getting to KNow New Database and Understand Where Relationships Are

I'm teaching myself SQL using MYSQL and a textbook. While working through the textbook I'm using a database I'm kinda familiar with - an exported copy of my CMS driven websites database. My website ...
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1answer
31 views

related column contents

I've designed a mysql database made of several independent/unrelated tables to use in my office. Different tables hold information about clients (names, addresses etc), visits to the office (dates, ...
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46 views

Bit column vs multiple join tables

I asked a question earlier about how I could define a many to many relationship between users and FOSes (fields of study). My original question was how could we know whether the user was the ...
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186 views

Multiple junction tables?

I am working on a system where you have users, and you have Fields of Study or 'fos' for short. Each user can have many fos and each fos can have many users. So we are dealing with a many to many ...