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

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7
votes
6answers
4k views

Best way to document database mappings for migrations [closed]

I'm working on a project that includes mapping database elements for a migration and I wanted to know what tools others were using to do this? Excel is a very flexible way to document simple ...
7
votes
1answer
158 views

Is it ever ok to not test a feature? [closed]

Is there any point at which you become so familiar with your language/database/system that there is no need to test a new feature/configuration/query/etc. by contained/simulated testing before ...
7
votes
1answer
160 views

Data Warehouse: How can i query daily snapshots?

I have some snapshots of a database that are not timeseries. For example: Snapshot day 1: +----+---------------+------------+------------+ | ID | Title | Category | Date | ...
7
votes
1answer
621 views

Temporal Validity and Primary/Foreign Key Relationships

I've read through several of the oracle tutorials that show temporal validity and time features. However, in the examples I'v read, there is no primary key used in the demo tables. ...
7
votes
1answer
429 views

CouchDB and document versioning

I'm currently working on a wiki-esque application using CouchDB and am trying to implement a document versioning scheme. The way I see it there are two ways of doing this: Store each version as a ...
6
votes
2answers
13k views

Efficient way of changing VARCHAR to NVARCHAR fields in a large table in SQL Server 2008?

I am aware of when adding new fields to large tables, it is recommended to add them to the end of the fields rather than somewhere in the middle, and wondering if something like this applies when ...
6
votes
4answers
529 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?
6
votes
2answers
412 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 ...
6
votes
5answers
4k views

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 ...
6
votes
4answers
768 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 ...
6
votes
2answers
4k views

What exactly is a database engine?

I have gone through the definition on http://en.wikipedia.org/wiki/Database_engine several times: A database engine (or "storage engine") is the underlying software component that a database ...
6
votes
4answers
444 views

Don't know how to transform variable entity into relational table

INTRODUCTION AND RELEVANT INFORMATION: The following example illustrates the problem I face: Animal has a race, which can be a cat or a dog. Cat can be either Siamese or Persian. Dog can be a German ...
6
votes
3answers
3k views

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 ...
6
votes
3answers
2k 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 ...
6
votes
2answers
3k views

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 ...
6
votes
2answers
1k 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?
6
votes
2answers
353 views

Am I violating any NF rule on my database design?

I am a newbie on creating database... I need to create it for my recruitment web application. My application needs to schedule screenings, exams and interviews of applicants and save result in the ...
6
votes
3answers
618 views

Help with a scenario of music groups and members in ERD design

Can someone please show me how to construct this ER diagram with the following scenario? I’m confused with the ‘or’ part of it. Description An Artist has a Name, and must be either a Group or a ...
6
votes
4answers
1k views

What exactly is overlapping candidate key?

Can some one please explain to me in simple terms what is overlapping candidate key ? What is overlapping as the name suggests? Consider the below relation R(L,M,N,O,P) { M -> O NO -> ...
6
votes
2answers
2k views

Best way to handle dates prior to 1000 A.D. in MySQL?

I am creating a database for records that extend prior to 1000 AD, but MySQL Date and DateTime fields only support dates starting at 1000. Is there a way that would be more convenient than either ...
6
votes
4answers
236 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 ...
6
votes
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 ...
6
votes
1answer
603 views

Convert clustered primary key to non-clustered and use another column for the clustered index

I have a large table with a primary key (GUID) that is also the clustered index. There is already a integer sequence based field. So I want to leave the GUID as the PK and make the integer column the ...
6
votes
2answers
4k views

Index max row size error

Is there a upper bound for an array column? I am getting this error when inserting into the array field - PG::Error: ERROR: index row size 3480 exceeds maximum 2712 for index "ix_data" Here's my ...
6
votes
3answers
288 views

Need help on my first ER diagram

I just started my first Database course online, and I have a homework assignment to create an E-R diagram from a list of specifications. The specs are as follows: The company is organized into ...
6
votes
2answers
486 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 ...
6
votes
1answer
4k views

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 ...
6
votes
2answers
2k views

Database Hardware and Software to handle million requests per second?

I'm curious about the necessary hardware and software requirements to support a strong MMORPG. For example, what kind of requirement (both hardware and software) would I need if I were to build a ...
6
votes
2answers
89 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 ...
6
votes
1answer
963 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 ...
6
votes
2answers
302 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 ...
6
votes
2answers
2k views

Recommended model for application level event logging

I am going to be storing application level events (user A added thing, user B updated that etc) for both public and private consumption. Below is an oversimplified model of the tables and their ...
6
votes
1answer
779 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 ...
6
votes
2answers
2k views

Unknown Db file format - best way to find out?

A client has given me the data he wants visualised in my project - but I don't know what DB format it's in. He's pretty unclear, also.. I have access to the table structures, but don't know how to ...
6
votes
1answer
859 views

LDF and MDF file sizes for a dynamically created Database

I am creating a dynamic database from C# code, and would like the database to have a fixed size (for example 5 GB). While creating the DB through code, I need to specify MDF and LDF max file sizes. ...
6
votes
2answers
1k views

nvarchar(max) converting to varchar and table optimization

I am working with a table that has all character types set to nvarchar some of them are nvarchar(max). We are converting all these to varchar and specifying a character width based upon the actual ...
6
votes
1answer
1k 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 ...
6
votes
2answers
495 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 ...
6
votes
3answers
1k views

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 ...
6
votes
3answers
442 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 ...
6
votes
2answers
934 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.) ...
6
votes
2answers
424 views

How many fields is too much for a primary key?

I am creating a table to store information about the placement of objects in a grid (game map). For example, I have a 10x10 grid and I want to store, in the database, that cell (5,5) has a blue box, ...
6
votes
1answer
2k views

need suggestions to improve view performance

I am looking to improve the performance of a view in SQL Server 2008. This view exists in a reporting database that is widely used by not-very-technical-folk to basically denormalize all of these ...
6
votes
3answers
3k views

Separate archive tables or soft delete for inventory database

I'm building an inventory database that tracks computer equipment and other hardware devices. At some point in any device's life it is retired and gets archived. After it becomes archived it needs to ...
6
votes
2answers
4k views

free database modelling software [closed]

What is available in the realms of database modelling software that is free. I am developing an SQLExpress database. CA ERWin - community version although is free, I can't see an option to allow ...
6
votes
2answers
4k views

Bit vs. Boolean columns

Given that bit fields are just binary representations of data and need to be queried in slightly "strange" way. Does it actually provide any benefit using a bit field for a boolean value? From what I ...
6
votes
2answers
2k views

How to implement soft deletes?

What is your method of implementing soft deletes in a database? Ideally the solution would allow for decent performance on large tables take relationships into account take unique keys into account ...
6
votes
1answer
2k views

EAV structure explained in Layman's terms

I've read several articles online that explain how EAV structures work, but there are different interpretations of them. Some articles mention that it's a representation of a data model metadata (or ...
6
votes
2answers
2k views

How can I save a severely fragmented database/table?

I've recently made a discovery that might explain my slow SQL run times. I found out that the default in SSMS is to allow mdf growth of 1MB at a time. When the size of one table alone is roughly 23 ...
6
votes
1answer
1k views

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 ...