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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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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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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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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719 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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283 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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900 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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188 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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4k 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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241 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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469 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
119 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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420 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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199 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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392 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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426 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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177 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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338 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
8k 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
407 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
111 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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106 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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90 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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480 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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735 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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84 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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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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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
243 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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666 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
4k 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
472 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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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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48 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
40 views

Best away to keep monthly records of loans

I'm trying to make a database to keep records of the amounts payed on a loan on a monthly basis. I already have tables for the clients, accounts, products and loans: create table product( id ...
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2answers
58 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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106 views

Copy table with separate sequences for serial columns

While creating a column management tool I came across the need to quickly replicate tables in PostgreSQL so I would not test new tools with non-test tables. To effectively test the new column tool ...
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2answers
38 views

Optimal indexing for SELECT (mysql)

What indexes would you recommend for the following select (and why)? Keep in mind there can be tens of millions of rows. SELECT * FROM mytable WHERE md5 = ? AND created_at >= ? AND created_at ...
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1answer
123 views

one table for all blob with a one to one table for metadata which link to one or many tables?

I'm going to start by saying that I'm not a DBA but i got that role in my current project so I'm doing my best. The application must be able to store files(attachments, official documents, etc) The ...
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1answer
87 views

Composite Foreign key to single primary key [duplicate]

How do I create a composite foreign key to a table with a single primary key? For example suppose I have the following tables: CREATE TABLE Branches ( BranchId UniqueIdentifier DEFAULT ...
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83 views

Unique column values between tables

I'm keeping track of teams and their members. Each team has one leader, one contact person, and any number of players, and each of them has a unique email address. The problem is that one physical ...
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198 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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1answer
748 views

MySQL - varchar length and performance

Is declaring VARCHAR size make sense for performance? Is there any difference (in speed) between VARCHAR(50) and VARCHAR(255)? Or defining length is logic/design constraint?
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1answer
51 views

Building dependence between regional data (Street -> City -> PostalCode -> Country)

I'm in the process of designing a database to contain regional data to be used inside a CRM system. So, a user suspects that things like the city or country are automatically filled (or maybe just ...
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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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3answers
240 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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1answer
84 views

Should I use a surrogate key in a mapping table?

I am deploying a mapping table which connects Items to ItemGroups Though an Item will only ever be in a single ItemGroup please accept a priori it is not appropriate in my use case to append a column ...
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86 views

How to store list of unknown size in database

I have trouble with database design and don't know how to overcome this. The problem is with list of cities between two chosen city. User chooses start and finish city, and OPTIONALLY, user can write ...