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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Performance of query with a range condition and order by

We have the following table (in SQLite on Android) which a tree structure (Nested Set model) of words and their frequencies: lexikon ------- _id integer PRIMARY KEY word text frequency integer ...
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356 views

Designing Simple Schema for Disaggregation of Demand Forecast

I am doing a simple database design task as a training exercise where I have to come up with a basic schema design for the following case: I have a parent-child hierarchy of products (example, Raw ...
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5k views

Importance of ER Diagrams

I am a student and I am developing several projects as a part of my academia. While developing the database for one of the projects, we came across a situation where we thought about whether ERD is ...
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Is there a tool to check if my database is normalized to the third normal form?

I learned about normalization recently, and understand how important it is when implementing a new schema. How can I check if my database is 2NF or 3NF compliant ? Manual review is a sure option, ...
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494 views

Purpose of IDs in a User Table Database

In a table, such as a user table, where there will only be 1 row with a for any particular user, why have an ID field, let alone as the primary key?
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365 views

What is the name of this schema pattern

Its been a few years... but I've run into a problem-set that reminds me of a schema design pattern and I'm trying to recall the details. Essentially, the pattern consists of one database which is 3 ...
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Pros/Cons Using multiple databases vs using single database

Working on a new project which has the requirement to use 7 databases. Arguing performance, stability, optimization is easier implemented. While I don't agree I'm having trouble collecting good ...
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587 views

How can a database be normalized when an optional field causes denormalization?

Suppose you have a warehouse full of widgets. Each widget in the warehouse is stored in a specific identifiable location within the warehouse. You might have a schema which looks like this: A ...
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Sharing a single primary key sequence across a database?

Is it an acceptable practice to use a single sequence as a primary key across all tables (instead of a primary key being unique for a given table, it is unique for all tables)? If so, is it ...
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Is one-to-one relationship normalized?

Consider we have a large set of statistical data for a record; e.g. 20-30 INT columns. Is it better to keep the entire set in one table as they all belong to a record OR creating a another table ...
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Can I add a unique constraint that ignores existing violations?

I have a table which currently has duplicate values in a column. I cannot remove these erroneous duplicates but I would like to prevent additional non-unique values from being added. Can I create a ...
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How to Handle TimeZone Properly in SQL SERVER?

I have some issue which needed to be fixed quickly. My local development server is in middle east. But my production server is in UK. Now, I need to show the date to user to thier timezone. For ...
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SQL Server Primary key / clustered index design decision

Looking for some advice regarding a table / index design decision I've got to make on some tables that I've got to port into SQL server from an existing 4GL based database. I've got a product history ...
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755 views

Increase all primary key values by 1

How do I increase all of my EmployeeID values by one if it is the primary key?
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841 views

Alternative to EAV for dynamic fields in a star schema data warehouse

I need to support dynamic fields and values in a big datawarehouse for storing API requests log, my user case is that I need to store all API requests query string and able to perform query against ...
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4answers
844 views

PK as ROWGUIDCOL or use a separate rowguid column?

There's a long-winded debate going on here so I'd like to hear other opinions. I have many tables with uniqueidentifier clustered PK. Whether this is a good idea is out of scope here (and it's not ...
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580 views

Can this business logic be enforced by a conditional database constraint?

I am trying to duplicate the business logic embodied an intranet C# web application in the database so that other databases can access it and work under the same rules. This "rule" seems difficult to ...
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Database for building a realtime analytics system

I want to build a system similar to Google Analytics (only used for internal use, less traffic and less feature), and mainly focus on Real time counting of unique URI visit/PV by different ...
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Visio 2010 and SQL 2012 - Reverse Enginnering

We have upgraded to SQL 2012 and Am trying to reverse engineer our Dbs into Visio 2010. I setup a connecting using SQL 11 driver and Visio complains that that driver is not supported. Any one run ...
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213 views

Dynamic contacts database

I'm trying to create a database for contacts. I must have many categories for every contact, like Home, Office, Emails, Phones. In every category one can add more than one value. Also the categories ...
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Why use separate databases for high traffic/volume tables?

While looking at the database structure of an application I am using I recognized that it uses 3 different databases on the same SQL Server instance for different things. The first one contains the ...
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690 views

What is the best database design for this situation?

I'm working on building a business application for my company and struggling to pick the most appropriate database design for a particular situation. Let's say I have the following entities: ...
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1answer
791 views

Are there any performance benefits to using a hash table with no clustered index?

I have this table: CREATE TABLE [dbo].[relatea] ( [mid] [varchar](16) NOT NULL, [sid] [varchar](16) NOT NULL ) It stores hash matches. Is there any benefit to having this as a heap? It has ...
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248 views

Design: How do you decide when items are related vs when they are attributes?

I've been trying to figure this out for a while. Let's say you have a person, for example. An attribute of a person is his or her social security number, right? But a person also has a social ...
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616 views

What makes an OLTP database an OLTP database?

This is a pretty broad question. I know the definition of OLTP. But it seems like unless you have an environment that has a clear distinction between OLTP and OLAP, in the sense of a database that ...
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2answers
260 views

Should I add a column or 1-1 table if property is usualy null

There's a new unique property we need to add, which is relevant only to a specific subset (less than 1%). We thought it's better to add a new table which will be 1-1, than to add a new column which ...
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2NF decomposition + database normalization

If anyone knows about 2NF I'd greatly appreciate if you could tell me if my understanding of it correct my book does not even mention it (except to say is of "historical significance") and I haven't ...
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446 views

Using 100's of schemas in a database SQL2008R2?

We are in SSAS type of environment with 100's of clients. Currently each client gets a database and we have 200 per instance on SQL Server 2008R2. This presents limitations with snapmanager being ...
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How to normalize Time Sheet data?

I am having a terrible time finding an appropriate way to store this data in a database. The current excel (simple) version looks something like this: http://i.stack.imgur.com/BEZOw.png Staff and ...
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1answer
375 views

Better to use a RANGE RIGHT or RANGE LEFT Partition Scheme

I'd like to know if it is better to use a RANGE RIGHT partition scheme or a RANGE LEFT partition scheme? Is one of these options by default a better choice, or is it heavily dependent on the actual ...
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3answers
192 views

Tracking changes on a table

I have a users table. I want to keep track of all the changes I have done,name,phone etc. I've thought to create an extra table changes that will store the id of the previous and the next version of ...
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2answers
840 views

Is it bad idea to create foreign keys on the tables in a different schemas in the same database for big applications?

I am working on the transfer a big pl/sql web-based application to the dedicated server. This application is located in one schema with 70 packages of programm code. This application was made ...
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2answers
650 views

Extracting entity from attribute in entity-relationship diagram

I am developing a database model where I need to capture information about rent contracts for parking places within a parking. I have thus defined an entity called PARKING CONTRACT. Requirements (r.) ...
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1answer
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What should every DBA know? [closed]

As a SysAdmin who "wears all the hats", I find myself increasingly pulled into database projects. I took one database course back in college and since then I've always scoured resources online (like ...
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545 views

Representing N:N relation as a functional dependency in a database design

As a software developer, I already have some experience in designing a more or less normalized database schema, but I haven't received any formal training in it before. This semester, I took a ...
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2answers
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Allowing Foreign Key to be Null

I'm trying to create a relationship between two tables where one column in TABLE A is the foreign key for a column in TABLE B. However, there is one row in TABLE B that is currently null in that ...
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1answer
189 views

Use multiple columns for location or supertype/subtype?

Given an Equipment entity, it has a location, generically called Whereabouts. This could be a reference to: a User entity (the employee who will use and be responsible for the eqipment for the next ...
6
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1answer
346 views

Dimension Help - Deciding Fact or Dimension

We have the following Dim and Facts: Customer Dim: SCD Type 2, Info about the customer ie first purchase date, name, address, etc Product Dim: SCD Type 2, about our products Customer Snapshot ...
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325 views

Definition for “logical difference”?

I'm currently reading "SQL and Relational Theory" by C.J. Date. And although I'm quite far in the book, I've got a few basic questions. I want to know what the term "logical difference" means, The ...
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1answer
395 views

How to store and query products the price of which depends on a complex set of conditions?

I haven't decided on a database. I have expirience with MySQl and I'm intrigued by MongoDB. Let the products be packages of cable tv providers: { name: "Virgin TV", price: 20 }, { name: ...
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1answer
244 views

Hierarchical structure with limited number of records per user

I am planning schema for an affiliate network. For all hierarchical queries I am using Postgres tablefunc extension but here is another problem. Any user can refer only 3 other users at max. So for ...
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2answers
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Bitmask Flags with Lookup Tables Clarification

I've received a dataset from an outside source which contains several bitmask fields as varchars. They come in length as low as 3 and as long as 21 values long. I need to be able to run SELECT queries ...
6
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1answer
160 views

What is a good way to determine the performance I should expect from a PostgreSQL server?

Trying to figure out how I should expect my database to perform. Basically, I need to determine when the server I have set up is reaching its performance limits - which would help me plan server ...
6
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4answers
375 views

Database Design for updatable sequential records

I am working on creating a data model for storing data related to production tracking. I work for an engineering firm that models and analyzes data for our clients. There are several steps in the ...
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258 views

Storing and querying rolling data in PostgreSQL

I have a large quantity of weather model data being put into a PostgreSQL database. The machine has 8 cores and 16 GB of RAM. I'm running PostgreSQL 9.3 with PostGIS 2.1. Each table will have a ...
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148 views

How to do a bulk load of a database when application are relying on it?

In a daily routine, I need to drop and do a bulk load of a database. The problem is that I have a WebApp relying on that database. So I can't drop the database just like this. What would be a good ...
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2answers
473 views

Introducing an 'age' category in a patients database

I want to do the following in my DB related to patients: when patient inserts his birthday it shows his age category as: infants, children, adult, elderly... etc. to help me classify my patients how ...
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3answers
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How costly is opening and closing of a DB connection?

How CPU intensive is opening and closing of a DB connection (for a web app) in MySQL ... when the DB software is on localhost? ... when the DB software is on another machine?
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386 views

How to design index for faster deletes

I want to speed up following piece of code delete from ssn_sdo where (art_id=@art_id and skl_id=@skl_id and @level=0 ) or (art_id=@art_id and skl_id=@skl_id and @level=1 and ...
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Is there a name for this “restricted one to many” relationship? Can it be enforced in the DB?

In an application I'm working on, we have a kind of "restricted one-to-many" relationship. I'm wondering if this has a name, and whether it's possible to enforce at the database level. A standard ...