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

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What should be the rule for excluding an FD from consideration while doing BCNF or any other Normalization?

Let us consider this example: http://www.mathcs.emory.edu/~cheung/Courses/377/Syllabus/9-NormalForms/examples.html At the first decomposition step, it is using A -> B C D E. On the next step, ...
0
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1answer
51 views

What is the best way to store SSH fingerprints and public keys?

I'm building a virtual Keyring in our DB to allow users to store PGP/GPG public keys with relation to email addresses so that they can optionally encrypt all communications our system sends them. I'm ...
0
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1answer
28 views

Scrapy data analyzed with R, mongoDB or other pipeline? [closed]

I'm scraping data using the Scrapy library in python and i'm planning to make few analysis in the future using R. In the future it could be a very big database with millions of items, what are the ...
3
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5answers
946 views

Database: One table or many

I am working on a project of classified ads site. I have 12 main categories, and their items are 142, Like vehicles have cars, scooters, bikes, etc. Mobiles Phones have mobiles, tablets, accessories. ...
2
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2answers
57 views

What are the prime and non-prime attributes in this relation?

R(HIJKLMNO) L -> MNO HI -> JKLMNO J -> KL K -> H HI is a key. So, H is a prime attribute. But, H is also in non-key part. What are the prime and non-prime attributes in this ...
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1answer
38 views

sqlite database table with 1000's of columns

I am using sqlite3 in an application to conduct an alalysis of distances between sets of points. Distances between these points have been precomputed using dijkstra's algorithim and left me with a ...
1
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1answer
58 views

Should I look into alternatives to a relational database? [closed]

I am currently in the process of going through some PHP training with procedural code and will be doing a course in OOP with PHP right after that. The course will provide a solid starting point for me ...
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2answers
87 views

m-to-n total participation in SQL

How should I model the following design in SQL? As it's shown, every A must have at least one B, and vice versa. I know I should have three relations: A(a), B(b) and R(a,b), but what about total ...
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2answers
58 views

MySQL - Order by closest value on multiple columns

I have a table for a game lobby. In this lobby a user gets put in their connection and their level. In my SQL statement I am getting all the users in the lobby which are between +5/-5 of the user's ...
1
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1answer
59 views

Efficient way to store multi choice in a column with few options

I am looking for advices on how to handle multiple choices in a column? By way of example lets say selecting a fruit for lunch. Options are Apple or Pear. And you are 100% sure those two options ...
3
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1answer
67 views

ER Diagram - subclass Entity constraint

Can someone help me out on how to model this situation: 1) Superclass PRODUCTS with subclasses FOOD and SHOES. 2) Another superclass CUSTOMERS with subclasses SHOE STORE, GROCERY STORE 3) I need to ...
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1answer
36 views

Database agnostic auditing [duplicate]

Background Various databases have custom implementations for auditing: SQL Server Audit Oracle Audit PostgreSQL Audit Trigger MySQL Enterprise Audit Problem A number of problems exist: There ...
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0answers
39 views

What is a good database design approach for my Online Quiz Android Application?

I have been working on an Android Online Quiz Application with PHP & MySQL. I know what attributes i need however when designing the relationship it becomes complex and confusing when I analysed ...
4
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1answer
47 views

2NF Normalisation

I'm using a past exam paper for practice, can someone help me normalise this database to 2NF? I have uploaded a picture of the original below, and also my attempt at normalising it myself. I am ...
1
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0answers
28 views

Design improvement on multiple references

Im having some 'perception' problem, maybe... I got this table linked multiple times with another small table and maybe is more of a personal problem with the way it looks but I feel there might be a ...
2
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1answer
55 views

SQL Query for Internal Messaging System

I'm creating an internal messaging system (No SMTP/POP3) and I'm looking for a way to query a user's list of messages. Here's my schema: Messages _MessageID (PK) _MessageParentID (if a reply this ...
0
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0answers
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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5answers
145 views

Should I have a column for every data type or 1 column that stores everything

I have a database table that currently looks like this: PageField -Id (Int, PK) -FieldType (String) Can be Text, Decimal, Integer or Bit -Value (This stores the value regardless of the FieldType, so ...
5
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2answers
341 views

CREATE as SELECT with CONSTRAINT?

I have a piece of SQL that creates a TABLE form a SELECT statement in PostgreSQL ; I want to add constraints to the table so that for example a column cannot be null. I cannot find valid SQL for this ...
0
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2answers
49 views

should I denormalize for user profiles?

Assuming the choice is to stay with relational model, how are tables structured in the case of large User profiles? All the examples I see consider only simple cases, such as a "profile" containing ...
6
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2answers
87 views

Which executes first? Trigger or rule?

Using PostgreSQL. Had a trigger which does something after delete and made a rule which stopped delete from happening if something will be true. My question is: will the rule prevent the trigger ...
1
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1answer
33 views

Animals hierarchy use-case: multiple farms, multiple species

Let's talk about an online service where goat/sheep/cattle/llama farmers would register and keep track of their animals. One of the features of such a service is tracking parent/child relationship. ...
4
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1answer
31 views

Dynamic form builder database optimization Postgresql

Hi I have a project that create forms dynamically I use a model like the following: forms ----- id (PK) name (other fields) form_fields ------------- id (PK) form_id (FK to forms.id) ...
2
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2answers
57 views

Multi level hierarchy relationship

My table design is users (id, username..., parent_id) Data is id username parent_id ------------------------------- 1 | admin | null 2 | reseller 1 | 1 3 | client 1 | 1 4 ...
1
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1answer
28 views

Update all rows when sort/ordering value is changed for single row?

I am in the process of creating a GIS application with multiple layers and many pieces of content shapes on each layer. Currently each layer/shape is drawn in the order that it was returned from the ...
0
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1answer
38 views

Query other database's INFORMATION_SCHEMA tables

I have a shared database that stores procedures for all the other databases on the same server. This helps maintain one instance of a procedure rather than copying it across all databases. As long as ...
0
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1answer
35 views

Joining 4 tables of which one is unrelated

I have 4 tables as follows. I want to find a wholesum resultset, limited to 25 records, in the following way: Users from Table1 based on a condition And those Users should not be in Table2 [Non ...
0
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1answer
36 views

Shared entities across multiple databases

I'm currently working on an application with a master database and individual user databases where all user input data resides. These individual databases are exactly the same. master connects the ...
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0answers
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 ...
2
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2answers
302 views

Can different tables have columns with the same name if those columns are not primary keys? [closed]

I know it's a simple enough question but my textbook is very confusing about it.
4
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1answer
48 views

Quite large (400k) mysql database design for multiple users

I'm seeking advice of experienced admins. I'm working on a website, where you solve word anagrams. If it solved it should never be displayed again. Wordbase contains ~400k entries. What would be the ...
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2answers
53 views

Document Store & Relational DB Hybrid. Exists? Possible?

Does anyone know of any product or open source project that attempts to strap together Mongo DB and MySQL for instance? I hear a lot about how relational DBs being ACID compliant makes it nearly ...
2
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0answers
22 views

Creating UNF for multiple actions

I am creating a database design for manufacture company for my coursework. The database design should be able to do these tasks: Buy items from suppliers. (M - N) Items are used for making products. ...
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6answers
856 views

Possible benefits of storing multiple values in one field of one row instead of as separate rows

During our last weekly meeting, a person that has no background experience in Database Administration brought up this question: "Would there be a scenario that justifies storing data in-line ...
0
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1answer
38 views

Best to isolate the database in multiple instances?

I read on a forum about the use of database isolated environments are neccessary for any large project that handles "big" data. For instance I will be using the following table for ALL blogs: ...
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1answer
67 views

Database Design and structure

I want to make colleges search system where a user enter any keywords in a search box and we can provide them some institutes with their details like institutes names, belonging hotspots, cities, ...
2
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1answer
42 views

For a software application, does every workstation need database drivers?

really a just a newb question. In the case of something like an enterprise system for a company, where end-users are executing continuous reads and writes to a database, it does not appear that in ...
0
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0answers
26 views

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 ...
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0answers
29 views

What is the db-structure behind sites with multiple similar subdomains, like Stack exchange?

own db for every subdomain 1 big db used by all of the subs own and shared db-s used by the subs When to use the 1st/2nd/3rd approach? Thank You!
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2answers
36 views

More tables or more columns (in my simple example)?

I'm modelling DB and wondering if I should create more very simple tables or just have more columns in tables. I mean, let's assume I have s table named User, each user can have status(ACTIVE, ...
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0answers
45 views

Database Design for group chat

I am creating a chat system as a RESTful API. This is what my design looks so far A request can be made to fetch the newest 50 messages that are part of a group id. Even if I do get a list of ...
4
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1answer
26 views

Enforcing that a user should have one or more email addresses

I'm trying to design an application where a user can authenticate oneself with one password and one or more email addresses. I'm not sure how to enforce this constraint. The tables so far are simple: ...
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0answers
36 views

Database calculations question

I am creating a MySQL database that is going to be used to store a lot of timestamps. There are currently 6 timestamp fields that data can be entered for one row. I am utilizing timestampdiff to ...
5
votes
1answer
111 views

Hard delete vs soft delete performance

I've got this table that is intended to have a lot of activity. Anything that's in it indicates that a user action is still pending. Once deleted, it would indicate that action is no longer pending. ...
4
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0answers
60 views

Social (Classmate like) database schema appreciation

This is a database schema I propose for a networking website like the Classmates.com web site. Do you think the database has all the tables needed for such a project? What would you rather do? The ...
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2answers
61 views

Is nvarchar 0-indexed? [closed]

Is the max length configuration for nvarchar 0-indexed, e.g. If I declare column x as type nvarchar and set the max length to (2): (X nvarchar(2)) does that mean that the column takes 3 nvarchars? or ...
3
votes
2answers
39 views

Mysql - Each mysql database with its own user?

I developed a web app in which each company that registers on the app gets its own database with its own mysql-user credentials. Is this approach fine OR can I use one master mysql-user account to ...
3
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0answers
42 views

Is this ER Diagram correct?

Requirements: • Each customer has a name, a permanent address, and a social security number. • Each customer can have multiple phone numbers, and the same phone number may be shared by multiple ...
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2answers
86 views

What are the advantages and disadvantages of Third normal form and Boyce-Codd normal form? [closed]

I know that 3NF makes a database more efficient and stores data according to relevance, which is more logical, but are there other advantages? and are there any disadvantages?
3
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1answer
80 views

Versioning data in a database [duplicate]

I have a database to hold data about projects. Projects have lots of data associated with them that is segmented into other tables such as project_contacts and project_images. Those are one-to-many ...