Database design is the process of specifying the logical and/or physical parts of a database. The goal of database design is to make a representation of some "universe of discourse" - the types of facts, business rules and other requirements that the database is intended to model.

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Many-to-one Subselection in single query

I have two tables with a foreign key from T1->T2, in a one-to-many relationship. That is, 1 tuple in table T1 is associated with 0..N tuples in T2. To create a simple example, lets say T1 is Cars, ...
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409 views

Messaging Database - How to handle multiple recipients

So I am trying to develop a relational database (I'm using MySQL, planning on a Java front end) where I have 3 tables (People, where I store names and relevant personal information... and Messages ...
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2k views

Postgresql vs MySQL - Which is better for join queries & writing data(inserts) [closed]

I have to design a database which will end up with 50M records in a single table(there will be other tables with lesser number of records). I'm more concerned with join queries & writing ...
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230 views

What is the meaning of this anomaly warning message?

I have run an analysis with SchemaSpy. The tool gave me a warning message for two tables. The warning message is: Tables with incrementing column names, potentially indicating denormalization ...
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201 views

Suggestion for storing a lot of simple data

I'm looking to crawl a lot of webpages (500,000,000,000) records and be able to store the linking structure for a later date. The way I planned on laying out the database was as follows: 2 Tables ...
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Designing a Products database: One Products table or many separated by vendor?

In order to prevent the unwieldiness of managing product data spread across a number of excel spreadsheets, I have set up a Products database. My data is in spreadsheets because it was (somewhat) ...
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448 views

Mysql error while creating FK

here is structure of both tables category table CREATE TABLE category ( `catID` bigint(20) NOT NULL AUTO_INCREMENT, `title` varchar(60) NOT NULL, `created_at` timestamp NOT NULL DEFAULT ...
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516 views

Reporting Database Considerations

We have a very large database that we want to write almost real time. We want to take data and move it to another instance of the database on top of which will be a GUI and MI tool which will be able ...
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623 views

Designing a database tables for the following scenario

I just got following entities Employee, Client and Company. Where Employee and Client have one to many relationship with Company ie A single employee may be mapped to attend to many companies and ...
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T-SQL insert value based on identity column

Is it possible to have a table with PK based on Identity columns? Lets say I have a table of customers, two fields are important for our case Id which is PK nvarchar(20) and SequenceId which is int ...
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58 views

Does a Key-Value type table still needs a auto increment key?

Suppose that I have a very simple table to store variable-like data, like this: +-----------+-----------------+ | key | value | +-----------+-----------------+ | site_url | ...
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66 views

Why WordPress use a column prefix? [closed]

I'm trying to learn some basic database design through open source projects. And look into the WordPress database schema, the posts table for example, you'll find something like this post_author ...
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244 views

Precautions when designing database schema if tables are going to have billons of rows

I am about to start work on telephone dictionary kind of project. Its confirm that there are going to be billions of records in dictionary table, and each entry from this dictionary table may have ...
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553 views

Modeling staff dimension in data warehouse

I need to write a data warehouse diagram. I've got a problem with staff area. I have to store a information about workers details like name, age etc., and workers job time and agreement details like ...
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1k views

How to handle huge table

We have a problem with a few tables that are very very big slowing down the system. so my question is if that size is normal for the amount of rows in the table, and also what could be done to make it ...
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298 views

One address table for many types of addresses

I have an application where I have to store adresses of multiple types of location. For example, my app requires addresses of people, hotels and event venues. Should I create separate tables for ...
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Choosing the right field data type in SQL Server 2008

I got a request to create a new table that will store certain information for customers. The definition of the table is somewhat irrelevant except for one field. This field will store ANSI characters ...
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4k views

how to Export a document contain tables name, columns names and column description from SQL Server 2008?

I created a db in sql server 2008 and I wrote for some columns description to describe them, What I want now is to find a way to export these tables design including the description for each column ...
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328 views

Best type to use in a composite key when one of the values varies in type

I am building a data store for the content of multiple blog sites which have been scraped. Each of these sites is going to have an entry in a Blog table BlogId Url ...
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251 views

How to convert MySQL Keyword to normal column

We thought of upgrading MySQL to new version 5.5.16. While testing the scripts with the new version, I had found one column Maxvalue is a Keyword in latest version. For this one, we need to change ...
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289 views

Where to save user data?

I hope this is the right stackexchange place to ask. Im really new using databases and I have a little question: Where to save the user data? I mean, if Im logged as "Foxandxss" on my app, and I want ...
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140 views

Oracle static lookup table

What is the best approach (or what options am I not aware of) to creating a static table or view where the data rarely, if ever, changes? An example use-case is a list of US states, where my ...
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60 views

How to design tables such that a person can work for many companies? [closed]

Database design such that a person can work for many companies?
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361 views

Best practice database design - user rating tables

I want to create a table to store user ratings of items for collaborative filtering algorithms. So far my table looks like this: IID | UID | Rating i.e. item ID |user id |rating. From ...
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162 views

Unique constraint to enforce max one null per item

I am using PostgreSQL 9.3. Suppose we are manufacturing some items of certain types, at any moment we are producing at most one item of a certain type. The following table captures our history of ...
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132 views

Creating a database with only MySQL command line?

The linux server on which I'm attempting to create a MySQL database has many difficult to work with permissions. My supervisor has tried to install MySQL Workbench on the server, but has been unable ...
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126 views

Data modeling with many attributes where few apply to each record [closed]

I'm pretty new to data modeling, so please excuse me if I've missed something obvious. I'm trying to decide on a schema (or possibly a DBMS) to work with some data where there are quite a few possible ...
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854 views

Slow delete caused by many foreign keys

My DB has about 90 tables. Most of the tables have an UpdatedBy and AddedBy column that have foreign keys pointing back to the user table. With even moderate amounts of data spread throughout the ...
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I don't know how to read many to many relationships

I'm reading this tutorial, and I have question about it. Look at this picture: Looking at Physical Many-to-Many Implementation I read the relationship this way: 'A user can be in zero or more ...
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143 views

Why do we not store names in a separate table?

Practically, I would never store names for customers in a separate table. But why not? It's a one to many relationship (a person can have one name but that name can be used by multiple people). ...
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5k views

Database design to track student attendance

I was having a doubt regarding the design of a database table to track students' attendance. Currently, my table students have atleast 4000 students. Creating a database for attendance to track their ...
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One or several tables for attributes

I just spent some time discussing two alternative DB designs with a coworker and I'm not convinced. Neither of us is strictly DBA so we may be missing something. The overall goal is to create the ...
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3k views

Oracle database created whats next? Create Schema or Create Tablespace?

I'm a programmer that's being thrown to the DBA/Sysadmin island all by myself with a volleyball that I named Wilson. I'm trying to survive here. I'm supposed to create a database for an application. ...
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430 views

Table for optional parent/child relationship

Assuming we have the following table: Item, Parent, Child and Parent is the parent of child. The item can either belong to a parent or child and not both. I have other tables that are similar to ...
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762 views

History table design for supertype/subtype

I'm designing an asset management database that tracks IT hardware. I decided to use a supertype/subtype design. I'm at a point where I want to track history of changes for devices. I wanted to use a ...
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2k 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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526 views

How to model a 1..1 Composition Relationship

We have a couple of entities/relationships of the following kind: Entity Event has a TimePoint The TimePoint contains time information about the event. It belongs to that event and cannot be used by ...
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286 views

Does this cause overhead ? Select name from User where user_name LIKE '%alex%'

I'm wondering if this statement can cause real overhead if many concurrent users send the same request to mySQL InnoDB storage engine. Let's say I have a table that has the user_name, and someone want ...
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444 views

Where can I find a good tutorial or book for various MySQL performance guidelines? [closed]

Can anyone refer me a good book or a small tutorial for various use cases for database design on MySQL for high load test/high availability scenarios. It should include the following: What are ...
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Where does a type specific field go?

Let's say I have table of cars and table of car manufacturers. Each car references one manufacturer. Furthermore, each car that has manufacturer x requires an extra field. Say, cars from that ...
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944 views

Database Design - Employee Clocking In and Out System

I want to develop Employee Clocking In and Out System (website). I am concerned two things: If staff forgot to 'Clock Out' from yesterday and they have 'Clock In' today, it should flag to the ...
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300 views

One to one relationship or another approach?

I need some addition thoughts on how to approach a database design I'm working on. The issue is I have three related items... * Clan (has many games) * Game (belongs to a clan, has many teams) * ...
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922 views

Can we decompose a schema into BCNF when it is not even in 1NF

Given a schema r(A,B,C,D,E,F) and a set of functional dependencies A --> BCD BC --> DE B --> D D --> A As we can see the schema is not even in 1NF as can be read here, now the question is can we ...
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313 views

Questions about Database Design for a Web Application

Consider a web application with 100,000 users. Each user can create blog posts. Assume each user has 100 entries. Would it be appropriate to store all the users in one table, with another table to ...
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150 views

How to enforce data consistency across one-to-one relationship in an inheritance hierarchy

Consider this design for a typical school database: Person: ----------------- FirstName LastName SocialSecurityNumber Phone Email Student: ----------------- Grade Teacher: ----------------- ...
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SQL Server 2012: set a column to only use a single case?

Is there a way to tell SQL Server 2012 to store both A and a as A (or both A and a as a) for some given column such that every insert statement does not need to have UPPER() in it?
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Is unique index better than unique constraint when an index with an operator class is required

Postgres docs say: The use of indexes to enforce unique constraints could be considered an implementation detail that should not be accessed directly. One should, however, be aware that there's ...
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937 views

Execution plan index suggestion - difference between similar queries

I am trying to analyze queries on this table: CREATE TABLE [dbo].[Values]( [tid] [smallint] NOT NULL, [t] [datetime2](3) NOT NULL, [v] [real] NOT NULL, CONSTRAINT [PK_Values_Unique] ...
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324 views

Removing chat history for a particular user from database

I'm currently developing a web chat application using SignleR and SQL server this is my database schema so far I've added an option where the user can Clear Chat history for a particular ...
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258 views

Relational Database design best practice

I am a student and I am trying to design a simple database, so if the ideas seem bad please let me know how to improve. I have three tables in my mind, one for Professors and one for Students. Both ...