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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Need a table schema for general store app [on hold]

I am Developing one application for online general store and stuck some where near making a schema for the products. Here, Every Product has brands and Product can come in multiple varieties like for ...
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12 views

master-slave vs masterless architecture [on hold]

As per Riak's doc "Most relational databases leverage a master/slave architecture to replicate data. ... Conversely, Riak uses a masterless system with no single point of failure, meaning any node ...
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1answer
28 views

How to keep updates (diffs) of some entity in the database

What is the best way to keep updates (diffs) of the some entity in the database? At StackOverflow we can edit questions and answers. And then we can look at any revision of the question or answer we ...
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0answers
10 views

Translating duplicated data entries into Domain Relational Calculus

Given a following table named BOOKING, which contains three columns, guest_name, room_number and booking_date, how do I find the all the guest_name that have the same room_number and booking_date? I ...
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20 views

Converting Entity Relation(ER) Model to Relational Schema?

I have the following ER Model I am trying to convert this to a relational database schema but I am not sure about several things: PORT_VISIT and PORT are weak entities. How do I figure on which ...
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10 views

Is the use of my lookup table efficient?

I'm trying to find the best way to architect the relationship in the scenario that: A team can have multiple players, a player may also have multiple teams My first thought was to use a lookup ...
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0answers
12 views

Data base design for handling website subscriptions

I have a website where at least 20 posts are posted in a day and each post contains more than 5 categories and each category has further tags. I wanted to build a subscription module that users can ...
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1answer
41 views

Suitable schema to record email sent and response received and invoicing in DB

When a form submission is made on a website: An email with form's details is sent to a set of recipients email addresses stored in a DB. The email contains a link for the recipient to show interest. ...
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15 views

Medical History - Is this DB properly design?

Could you please tell me if this DB is properly design? Are relationships type correct? Is there anything I should delete or add? Thanks you all very much!
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0answers
40 views

Database schema design for individual configurations

I'm trying to design a database schema that allows me to store customer custom built products. As a simplified example: A user can buy a cupboard, draws, boxes, and dividers. A cupboard has 2 tiers. ...
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1answer
30 views

Help with relational database design

I have a data model where each user profile belongs to a department. Each job is also available for a specific department. The department names are formatted like this: AAA-BBB-CCC-DDD-EEE, but of ...
2
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1answer
77 views

If A and B are candidate keys, then AB is candidate key or not ?

If R{abc} is a relation, f{ a->b b->a a->c b->c }, then a and b are candidate keys. What about ab ? Is it a candidate key or is it a super key or both ?
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40 views

MySQL Query Causing Massive Slowdown Over Time

I've been experiencing massive slowdown on my server after launching a new website. Using MONyog I can see that after an apache/mysql restart, the queries/second starts out nice and low for around 10 ...
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22 views

Database systems with users and sub users accessing the data

I am making a database for school student maintenance. Below is the basic description. There are schools. One school has many staff (i.e: Principles,Teachers, Section Head, Office Staff etc) These ...
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34 views

Designing a correct table structure

We are trying to save the Family History of a particular foreign job applicant. Below are the details we have to save. Familiy Member: Father|Mother|1st Brother| 2nd Brother| 1st Sister| etc etc ...
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21 views

How to have a relation applied only to all entities related to another given entity?

Let's say I'm trying to design an online server for judging a bunch of submissions to several problems. Firstly, each problem has many subtasks (which must go to one problem alone). For each ...
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1answer
63 views

What's the best database if i want save data temporally? [closed]

I want to create a datalog system so I need to store some int data temporally. What would be the best database (Relational, NO-SQL or some specific) for that purpose? And what would be the best way to ...
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0answers
30 views

In terms of relational databases is a Relvar the equivalent to a Schema?

I've been reading up on relational databases and the term Relvar and schema keeps coming up. From my understanding: A relvar is a variable holding a relation. A schema is a logical definition of a ...
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62 views

How to design a Many to Many relationship table?

I'm new to DB's, so I'm not really sure how to even formulate the question. Please feel free to edit the question itself. Anyways, let's describe! I should advise that I am using MS-ACCESS for this ...
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0answers
68 views

Storing URLs in a database

I am thinking about storing URL's in my database, but I am not sure whether the way I use is an efficient way to do things or not. Table name : url url_id (Primary Key & Auto Increment) url_value ...
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0answers
47 views

What are the different types of binary relationship types?

I'm new to databases and while studying questions on it, I've come across one that I can't find the answer to. Define the three different binary relationship types that are common in relational ...
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1answer
75 views

How to insert values into a junction table?

I add values into my two tables using the code below, but I also have a junction table called book_main_cover and I want to add data into this table to make a connection between book_id and ...
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1answer
19 views

Relation between tables [closed]

This question may be too easy to ask, but I can't understand how to do it. I am new in SQL. I have two tables. Table I book_id (AI & Primary Key) book_name book_year Table ...
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1answer
624 views

Create relationship between two tables with composite primary key

I've created a table [t1] with two fields and a composite primary key, show in below: create table t1( id int, name nchar(10), primary key(id,name) ); I want to create a second table ...
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2answers
74 views

SQL Query: Selecting a person who is a member of all existing groups

I'm tinkering around with my very first SQL queries and am completely baffled by a problem I encountered. Let's say I have the following database: PERSON(PID, Name) MEMBER(PID, GroupID) How would ...
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21 views

reports on history table

Assume Trucks which travel between Cityies. I store the Cityies that a Truck has traveled to in TruckLocationHistory table, if the Truck is passing the City, State = Passed and if it gonna stays for ...
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1answer
310 views

MongoDB Manual References vs DBREF

I've been researching MongoDB and trying to see if it would be a fit for my company's product catalog. I came across database references: http://docs.mongodb.org/manual/reference/database-references/ ...
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2answers
249 views

MongoDB/MySQL - auto increment vs object ID

I am in the process of evaluating MongoDB and writing some basic PHP applications around it. Typically in my PHP/MySQL applications, I would create an ID field and set it to auto-increment on each row ...
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1answer
41 views

Help with preventing double bookings with variable lengths

I'm designing a sample database for a venue where members can create bookings for venues. I'm looking for a method to prevent double bookings (possibly by creating a button on a form that checks ...
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35 views

calculating Canonical covers

Given F = {AB -> C, A -> BC, B-> A}, compute Fc AB-> C is A extra? {B->C, A-> BC, B->A} 1st possible Fc = {A->BC, B->AC} AB-> C is B extra? {A->C, A->BC, B->A) 2nd possible Fc = {A->BC, ...
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1answer
59 views

Help writing the following query to relational algebra

Can someone help me in writing the following query to relational algebra, I am studying DBMS and I am stuck on this exercise. Query: SELECT a.name, d.name. d.grade FROM student a, enrolled i, class ...
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3answers
96 views

Database Design for Paper Submission System

I am learner of Database design, I want to design a database for a journal paper submission system in which one paper can be submitted by one or more author. I have initially two tables Author and ...
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1answer
496 views

How to insert values in junction table for many to many relationships?

I have three tables in database: trips(trip_id(pk), trip_name(unique), user_id(fk)) places(place_id(pk), place_name(unique)) trips_places_asc(trip_id(fk), place_id(fk)) Since many trips can ...
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2answers
60 views

Need help about giving relationships in database design

I am developing a simple blog application in which users can write posts and others can like, comment, share etc. i am facing difficulty in designing database. What I have tried is: user ...
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1answer
73 views

Trying to map postal codes to their respective cities, but running into some issues

The Problem I am creating a database of Countries, Regions, Cities and Postal Codes. Here's an example to give an idea of the database structure as it is now: Now, let's take Tuskegee University ...
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1answer
48 views

Transforming a relation to 3NF

I'm trying to transform the following relation to 3NF but can't figure it out. The relation is (a student can only have 1 major): STUDENT (StuID, StuName, Major), Primary Key = {StuID} I tried the ...
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3answers
60 views

Study material for Advanced Databases module inc SQL, Relational Model, ERM & TM [closed]

For my next module in my masters, I am planning on studying Advanced Databases. (Long story short, the masters is designed for people with NON-CS degrees, so I have never studied databases, therefore ...
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1answer
106 views

A question regarding the performance of normalization

I am sorry this is such a newb question, but it is one thing I am having a difficult time wrapping my mind around, and after an evening spent reading I finally just decided to ask for some ...
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0answers
49 views

Multi-Tiered Database Design Issue

I am trying to build the multi-level model as demonstrated. When a user creates a campaign they will select some categories and some metros from tables Category and Metro. Those selections will then ...
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3answers
531 views

Replace relational database with “poor” design in software product with non-relational DB? [closed]

Edit: This question is about how to deal with many issues that arose from a overall system design, which made parts of the system deviate from common standards. For example, managing everything in the ...
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2answers
196 views

Relational Model vs. Database Products [closed]

The formal Relational Model (logical level) for databases is not exactly the same thing as you get with MySQL, Oracle or other major products / implementations of ‘relational’ database management ...
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0answers
27 views

Employee permissions in ER model

I'd like to model an approach to permissions which I can visualise in code but am a little blurry about on the ER side of things; Each user will be logged in at this point and bound to a record ...
2
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1answer
32 views

Is it possible to enforce a Unique Constraint on a Dataset comprised of joins

I am playing around with an idea to describe friendships in a system, and I am wondering about constraints. I currently have a database that looks like this: Users: ...
2
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1answer
87 views

Inheritance or lot of relationship?

I have to transpose a class Diagram into a Physical Data Model (more precisely MySQL database structure). In my class diagram, I have a lot of entities (A, B, C, D) which inherit from an other ...
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3answers
68 views

Best approach for Legal/Natural can have many Orders

I'm working on this model: where as you may see one NaturalPerson can have many Order and the same for LegalPerson the only difference between NaturalPerson and LegalPerson are a few so in that ...
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1answer
39 views

Modeling global and private parameters

I'm trying to model a database that will be used for management and execution of SSIS packages. The entities are Client, Job and Package. A Job is the managed unit that references Client and Package. ...
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0answers
64 views

Relational or non-relational database for a system to pass objects on?

hopefully this is the right place to ask this kind of question. I am working on a system that focuses on helping people give away things that they don't use anymore. So, an object typically has the ...
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1answer
48 views

Schema check or “DATE as separate table”

I'm dusting of my SQL, and would love to know if I've got my mental ER-diagram right. http://sqlfiddle.com/#!2/c5c59 Basically, I've got 10-15 different datasets (actividades) from several locations ...
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1answer
256 views

Beginner questions about SQL and relational algebra

I'm doing some exercices waiting for the exam. I have some doubt. RELATIONAL ALGEBRA These are the table: Newspaper (Cod_n, Name_n, Publisher) Article (Cod_a, Title, Topic, ...
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2answers
152 views

Logical problem with a database model

Beforehand the table names and columns are in Spanish, my native language is Spanish. (table names have been now edited to English) I've got a database to manage the tickets sales of a trip that is ...