The logical model and/or physical design of a database.

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testing an extraneous attribute in a relation using functional dependency

I am studying the book "Database System Concepts" by sudarshan . In chapter 8.4.3 in a dependency alpha->beta , If A ∈ aplha to check if A is extraneous, let (gamma = alpha − { A}), and check if ...
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524 views

How to represent directed graph with multiple parents?

http://dirtsimple.org/2010/11/simplest-way-to-do-tree-based-queries.html provides an algorithm for inserting and deleting from a Closure Table. I'd like to model a similar data structure, except that ...
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122 views

DB Design: Looking for Performance improvement with a Column used in all SQL Queries

I recently got added to a new ASP .NET Project(A web application) .There were recent performance issues with the application, and I am in a team with their current task to Optimize some slow running ...
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85 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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379 views

How to handle many columns / variable schema?

I apologize in advance in case this question has been asked already. I'm working on revamping a reporting application used within my company. The requirements are: Support addition of new fields ...
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265 views

Conceptual model vs Logical model vs Physical model

I'm doing a work about database, and now I need to show three different images, one image with the conceptual model, other with logical model and other with physical model of a database. I'm looking ...
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155 views

Dealing with Multiple User Roles

I'm working on a project based on a CMS, where there is a built-in roles table. However, the CMS allows a user to have one role only using role_id And these are the requirements that struggling me: ...
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27 views

Optimize finding the next batch of data from A to be crunched and inserted into B

I'm using PostgreSQL to store data produced by a large distributed computation. There are several stages to this computation; the idiom we've settled on is that there's a table containing the results ...
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165 views

“Replicate” Table structures with sp_addscriptexec

In our customers environment is a massive central server (running SQL Server Enterprise 2008R2) and some distributed PCs (running SQL Server Standard 2008R2). The central server has a replication for ...
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553 views

Postgresql - How to Convert all Column Names to Lowercase

I have a travel survey with a series of tables (lots and lots of columns) that I exported from MS Access into a postgres database. I've search around a lot for an explanation of how to convert all the ...
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23 views

Modeling for inclusion of two different entities

What I Have I am currently hashing out the data model for an application that will utilize MongoDB. In my setup, users or members (as they are called in the schema) will be created and then assigned ...
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775 views

How to generate data for News Feed efficiently like facebook , googleplus , twitter e.t.c?

I have created table as post ( post_id int(15) auto_increment primary key , user_id int(11) , post_text varchar(2000) , post_type int(1), ...
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26 views

Difference in the workload related to data-amount and search option

A couple of days ago I was asked why it is necessary to use the first normal form also for separation of names. We have a table which stores private customers (Name+Surname;Information) and business ...
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2k 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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42 views

Basic Design Question about one to many in a table

Sorry for the basic question but I am new to all of this! Say I have a table named Runs, and each table has Run: id (primary_key) data (String - path to a data file) status timestamp ... ...
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41 views

Second opinion about elimination of possible redundant database column

We currently have a Widgets database table were we track the widgets the company produces. When a widget is produced the widget information is added to this table. This Widgets table contains a Status ...
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34 views

A better model for connecting users to different objects, even efter they cease to exist

I've got the privilege to create a small in-house application for managing todo-lists, although I am not really a developer. (I know some PHP and SQL, and got a chance to prove myself). As my ...
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134 views

Can somebody check this normalisation workings i think i am missing a step or a dependency somewhere

given these two tables: and: I need to first list them as an un-normalised structure(s) then i need to identify the functional dependencies/primary keys. Once i have done this i must represent ...
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216 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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35 views

Keys of a relation

I got relation: R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)} keys of this relation are: {BCE}, {EF} But i dont get it... why? Why not only {EF}.. it got less ...
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1k views

SQLite Design: Better to have many tables with few columns or few tables with many columns?

I am struggling to figure out the best design for a Sqlite database that will hold data about Facebook pages so that I can calculate benchmarks for how the average Facebook page performs. I have an ...
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128 views

Best practices for ranking records in flexible way

Suppose we have 10000 records of any product. User search on our website with his given criteria. so we output search results based on given criteria. Now Admin want to rank products in search. so ...
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200 views

Relation between lossy decomposition and Natural join?

I am confused with the lossy decomposition and natural join. Natural join(with common attribute): only respective common attribute for the resultant table is formed. Lossy: Natural join on tables ...
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28 views

Optionally free-form reference

I've seen a few instances of entities which have a field which can be either a reference to another entity or free text. You typically represent this in the UI by having a dropdown widget which can ...
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349 views

The correct way of representing folders

I'm trying to kind of emulate a folder structure in my application. Now I've thought of two ways to achieve this, but what is the best practice for that? Table: Attachments Columns: Id (PK), ...
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495 views

How to store object with property of generic type in DB

In my business domain there exists an entity parameter. Beside other properties which are identical for each parameter, they have values. These values can be of different data types. There might be ...
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136 views

Are duplicates ever acceptable in a database

A warehouse system I am working on allows inwards consignments [type = 0] and outwards consignments [type = 1]. The user selects multiple products for each consignment and then multiple warehouse ...
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50 views

Where should a default setting field be?

I am creating a database to track occurrences of incidents on buses based on an existing system. Currently the drivers can set a default bus number, which is used to pre-populate the bus number on the ...
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463 views

Data modelling: RBAC for small enterprise software

I'm building the core tables for a small, cloud-based enterprise app. Is this data model suitable for a role based authentication system (flat hierarchy of permissions) that allows users to work for ...
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328 views

When to split a large table

I run the SQL Anywhere DBMS, and we have a table of about 10 columns(normal text, timestamps etc). However, in my use-case, every single day, the table gets 2160000 new rows. It's also crucial that ...
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337 views

Database Design: separating reusable & instance data

I'm developing an app which is basically a collection of checklists that have to be processed. I obviously need a database in which the information has to be stored. I just can't wrap my head around ...
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146 views

Real Time data collection - Help select Database

My Scenario: I want to collect data from various sensors[for now I have 600 sensors sending data, but this may have to scale up to 3000 more data sensors, all sensors send real time data] Now I have ...
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834 views

How to represent class table inheritance (current DBMS-specific way please)?

I want to implement class either-or table inheritance (Account, CatAccountDetails, DogAccountDetails) in SQL Server. I found a recommendation for MySQL here (How do I map an IS-A relationship into a ...
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112 views

Unable to decompose this relation to BCNF

I have a relation R = { A, B, C, D, E, F, G, H, I } And functional dependencies F ={ ABC -> DE E -> C AB -> F C -> G F -> H H -> IJ F -> B } I am able to do simple BCNF ...
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130 views

key value database

I have one object and a lot of data associated with that object, you can think of it as something like facebook timeline where we have user and user has a lot of posts. I cannot store data in JSON ...
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276 views

Improving database design for category based site

I'm working on a site that gets about 30k visits a day and it makes use of a lot of queries which uses UNION's over about 45 different tables, these tables generally range from about 15k rows to about ...
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Question on comparing two fields in Access

I'm not sure if the title is fitting as I am not 100% sure if what I am doing is correct but here goes. Here is my enrolment table, I have added a field called pass/fail as you can see which is ...
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How can I make microsoft Access update fields that are linked in several tables?

I am working on a database for clinical observations in cancer mouse models. Usually, the animal care staff reports an observation that the vet checks. Sometimes, we have false positives that I need ...
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35 views

Are my two proposed solutions on modelling resources inventory decent?

In the project management system that I am developing, I am wondering what is the best database design for keeping track of the resources inventory. While I want to determine what resources are ...
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29 views

Sql multiple table checks for polling

I am implementing long polling using mysql for a near realtime data update for clients. Currently, this is what I have (and it works): A messages table, that holds messages between users,there is a ...
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21 views

Schema Design for multiple many-to-one relationships. of which exactly one should exist

Say I have table A, B, and C. B and C can both be related to multiple A's, but each A should have exactly one of either B or C related to it. Which database design is better: A: a_id, b_id NULL, ...
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16 views

Sum data from 3 tables(joining), but one of may no data then other tables data will show

I am making a stock group summary report for this I am making Sum data from 3 joining tables, but one of may no data then other tables data will show. I have 3 tables as: ac_stock_item, ...
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27 views

Is this solution correct?

We have the final relations of a database: Worker ( ID_W, Name_Lastname,Obligations, #ID_D) Department ( ID_D, Name_D) Vacation ( #ID_W, #BeginningDate ,Length_days) I have to draw the Conceptual ...
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30 views

Is double one to many a bad design? It looks duplicate when joining both one-to-many tables

Suppose I have user table, book table, DVD table. User can borrow n book, n DVD at the same time, a book or a DVD can be borrowed by a user. (I understand it is many-to-many situation in real life, ...
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19 views

Remove a parent entity in PowerDesigner

I have User table in a PowerDesigner logical model, which inherits from a base entity that has Id as int. I need to change this to string. I can't change the base entity's id type, as only one table ...
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12 views

Table mapping _ updating

I have three tables with inserted data so I want to update Value.Value with H.facility and H.Dep and H.CAT. Actually table V is the metadata of table H and table value has FK to V. I want to ...
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28 views

DB table structure for many-to-many relationship

I'm trying to develop a relational DB design which stores data related to aerial survey(s) conducted off of the coast. The DB stores the actual data collected, as well as design parameters. The ...
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32 views

Relationship between favorite and contact in database

I am making an E-R diagram for my contact project that simply has contact and favorite as tables. Both of them has the same attributes(ex:id,name,number). What is the relationship between such ...
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43 views

Updated Financial Database Design

I took the design that @Daniel Hutmacher suggested in question below: Financial database design I amended it as to what I need below: -- Companies CREATE TABLE companies_list ( [code] int NOT ...
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DB table design for attributes with multiple entries (eg: Person -> Social Media)

I am trying to decide the structure of a DB table to store Employee data. I am bit confused on how to design attributes such as Address, Social Media etc. There should be provision for multiple Social ...