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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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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510 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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285 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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442 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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125 views

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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894 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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3answers
299 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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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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911 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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312 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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109 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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59 views

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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104 views

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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1answer
801 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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3answers
300 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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3answers
250 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 ...
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986 views

Many one-to-many relationships between two tables

In the process of creating a small database for a therapeutic boarding school with Access 2013, I have a problem when designing the relational database model. Two times at least, I ran into a ...
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1answer
193 views

What's better here - a single column or multicolumn primary key?

Let's assume you have a table groups and a table item. Each item belongs to exactly one group. It is an inherent part of that group. An item cannot exist outside of a group and it cannot be moved to ...
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5k views

Database design for eCommerce website with multiple products having huge specifications index [duplicate]

I am designing a web site for online shopping and I have a question related to that. As you know that shopping website may have different product with different statistic/specification. What is the ...
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247 views

Concept, ER model, “employee tracking”

I have to achieve 3NF with following specifications: Database where I will determine priority skills for specific jobs and track the employees ability to complete them. Train employees. Example of ...
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522 views

Autoclose property resets to true after attaching db even if model is set to false

I am using SQL Server Express 2008 R2. The auto close property of a newly created database will be set to value same as model db. In my case I have set autoclose to false for model so that when I ...
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4answers
130 views

Better Indexing for MySQL?

Is it better to index each column individually with it's own key or to index multiple columns under the primary key? I've seen it done both ways in many different applications and I don't see a clear ...
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426 views

Constant values in columns

I have a SQL Server 2000 database used by our ERP system. There are many columns that always have the same value. A table row is really huge, potentially exceeding the maximum row size in SQL Server ...
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1answer
78 views

When do you add your foreign keys?

I'm scripting out a fairly simple database so I can simply hand off a script to someone else for an application to use. I'm curious about where best practice/the community stand on this: When should ...
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1answer
208 views

Is it better to use multiple one-to-many relationships, or polymorphic?

I've got the following tables: Clicks table Websites table Ads table Both Ads and Websites have many Clicks (i.e. both models have a one-to-many relation with Clicks). In such cases, is it better ...
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401 views

How should I store multiple relationships (many posts to many categories)?

I have posts stored in a posts table and I want each post to have multiple categories, what is the most efficient way to store the categories and their relationships ? I thought of it this way first: ...
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443 views

Unique Constraint with multiple null columns

I have two tables PC(Id,EmpName Not NULL, PCName NULL, HostName NULL,.... PhysicalLocation NULL, PCType Not NULL) PCNetwork(Id, EmpName Not NULL, PCName NULL, HostName ...
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180 views

Multiple primary keys

I am new to database design and have been looking at some example data models here. One thing I don't understand is if you have a table like client_addresses from the link above: ...
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1answer
361 views

Conceptual Design of a data warehouse (declaring the grain)

I am trying to design a data warehouse using this example scrubbed data. I need to declare the "grain". I know its the lowest level of detail in the fact table, but I am having a hard time determining ...
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5answers
9k views

Coding an accounting database from scratch? [closed]

My new medical practice is picking up fast and my homemade Libreoffice Calc spreadsheet is quickly becoming cumbersome to track patient visits, accounts receivable, overhead reconciliation, etc. Most ...
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3answers
421 views

Design for archiving a sorted list (with ability for a few INSERT)

I have a somewhat static sorted list of words which I want to save in a database table: -- simplified! -- Note: the rank/order of each item is NOT calculable from other values! CREATE table words ( ...
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1answer
113 views

Issues with a Table having 120 fields in mysql

I am creating a table with 120 fields in MySQL. It will have 50 varchar(255) fields, other are maximum fields with char(1) , 1 date field and 5 double fields and others are int(11) fields. My ...
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3k views

Conversion of statements to E-R Diagram

EDIT: PLEASE DON'T CONSIDER ARROWS :) statements are "A teacher can teach many courses. A student can enrol in many courses. A course may be a part of one or many programmes. A teacher can be ...
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48 views

How to constrain data

I have 3 tables which are related and a constraint on one of them which I can enforce in software but I don't know how to enforce in the database. I have a series of providers who send a set of data. ...
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107 views

Table Design - Identical tables for different statuses

I am developing a transactional System and the below is a simplified scenario of my problem. Users enter JOBS in a system. A User first enters a JOBS with a DRAFT status (and the Job is given a ...
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1answer
91 views

Tables of a huge database

When I work on a huge database, and after following normalization rules, I found that I have many tables for each part of my huge database. That makes me worry about the final number of tables, it ...
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1answer
525 views

How to set unique columns combination

see this table: CREATE TABLE IF NOT EXISTS `default_messages_users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `message_id` int(11) NOT NULL, `owner_user_id` int(11) NOT NULL, `to_user_id` ...
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753 views

Single or multiple databases?

I am in the progress of designing a database (or databases) for somebody and since I am a beginner I would love some advice. The data is described as: Customer1 (c1.type1, c1.type2, c1.type3) ...
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3answers
85 views

Decorating an existing database table with information that no one else cares about

We have a table that many processes read from. Some of them want to keep track of the fact they have processed this data, whereas others simply rely on fetching the data from the table based on user ...
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1answer
125 views

Where do caching servers conceptually fit in my architecture?

Given the simple well-known architecture below: Where (conceptually) does the caching server(s) sit?
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1answer
178 views

Splitting a table based on business logic

This is mostly a design question and I'm looking for any feedback about the merits or flaws of this approach. Typically, I break database design into two categories, Business Logic and Recorded Data. ...
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1answer
249 views

Guidance on simplifying the following diagram

I have a case scenario where a customer can book accommodation or flight only or both. I have modeled the accommodation part, however i am making things complex by over-thinking how stuff works in ...
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1answer
675 views

Does composite cluster index affect performance of seek/scan non-cluster index which is part of the composite?

I have bank transaction table with columns Division Brcode TrDate ProjectCode Accountnumber EffectiveDate DrCr Amount EndBalance In the other table the Brcode itself is unique and is assigned under ...
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1answer
5k views

Set permissions on all objects for SQL users

I have a procedure that loops through all objects in the database and assigns them proper permissions to that object. I want to know if there is a better way to do this? I use a model database to ...
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2answers
480 views

Determining sizes for Separated Partitions of programs, data and logs in SQL Server

As per the recommendations of the CIS benchmarks for SQL Server, I want to create separate partitions for the data, the programs and the logs on my SQL Server dedicated server. Question is, what is ...
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1answer
188 views

In a recruiting website, should I force a choice between one table for jobseekers and employers or 2 separate tables?

I'm working on a recruiting web site and I was wondering what would be best between: 1) A User table, the employer accounts are linked to a company (therefore when companyID is null then it's a job ...
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2answers
34 views

Should a table have a foreign key to another table if it already has a foreign key to another table that has that foreign key?

That was a hard title to digest even for me so I'll break it down. I'm very new to SQL, and I just designed my first database. I also am not very good at JOINS which might be the answer to my ...
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1answer
55 views

Name for intermediate aggregated data [closed]

We have raw data and aggregated data as well as sometimes multiple levels of aggregation between. Is there a name for the data in that intermediate "state" of aggregation? Just like how we have Real ...
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1answer
50 views

Make 3 separate tables, or 1 combined table for similar data?

When designing a database's structure, if we have multiple tables with similar data, should these tables be combined, with an added ENUM field to denote the table type; or should 3 separate tables be ...