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

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6
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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
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
501 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
2answers
4k views

Which datatype to store XML data in: VARCHAR(MAX) or XML

I am defining a schema for a new set of resources using SQL Server 2008... In this case, each record (e.g. row) will need to store XML fragments. From time-to-time; although not frequently; I'll need ...
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
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3answers
512 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
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2answers
1k 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
473 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
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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
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
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2answers
3k 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
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2answers
6k views

MySQL Database Schema for Train Timetables

I am interested in what a MySQL database schema would look like for a train timetable. Generally this is presented in table format as the final result. Train No. 11111 22222 11111 Train Day ...
6
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1answer
7k views

Ternary relationship: what's the difference between having single table and having multiple tables?

Consider the following ternary relationship: Suppose that all entities have only two attributes (PK and Name). Here are the tables I derived (5 tables): Sector ------------------------- ...
6
votes
1answer
744 views

How does PostgreSQL physically order new records on disk (after a cluster on primary key)?

Need to know how PostgreSQL orders records on disk. In this case, I would like to take advantage of index combination as stated in the docs, which as I understand uses bitmaps to get matching rows ...
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 ...
6
votes
3answers
875 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 ...
6
votes
1answer
144 views

PostgreSQL and table inheritance

I'm not sure if this is the right place for this, so please feel free to tell me if it is off-topic or there is a better place to post. I am working on a fantasy sports based project, and the number ...
6
votes
2answers
2k views

Will table inheritance in PostgreSql suit this situation?

Let's start off by saying, I'm new to PSQL and coming from a MSSQL background. I'm starting to design a DB in PSQL. So my main aim is to have a Main schema in this DB, which I am going to use to ...
6
votes
1answer
2k views

SSIS package with BULK data load

I analyzed a C# program over the weekend for a customer that basically does the following: Truncate Table Fetch Data (source on these is either remote database or local database where job runs) ...
6
votes
2answers
12k views

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 ...
6
votes
2answers
1k views

How should I model an “either/or” relationship?

Say I have an entity named Software and two sub-types FreeSoftware and NonFreeSoftware. The NonFreeSoftware entity has attributes such as purchase date, vendor, etc.. The FreeSoftware entity has ...
6
votes
1answer
213 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
votes
1answer
391 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 ...
6
votes
2answers
473 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 ...
6
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1answer
502 views

Can filtered indexes help improve queries that are based on a time entered or should this be avoided?

I'm just learning about the new filtered indexes in MS SQL 2008 and I'm trying to understand where they would hurt and where they would help. I can see that adding a filtered index to an employees ...
6
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2answers
132 views

Creating relationships between tables that where not specified in the given UML diagram

Good evening! I'm working on designing my very first actual database from the following UML class diagram (in French unfortunately): I'm at the point of creating the relational sketch of it which ...
6
votes
1answer
5k views

Database design: Two 1 to many relationships to the same table

I have to model a situation where I have a table Chequing_Account (which contains budget, iban number and other details of the account) which has to be related to two different tables Person and ...
6
votes
1answer
1k views

Pros and cons of using many schemas in PostgreSQL as opposed to just one?

For a large SAAS application (backed by PostgreSql 9.4), with over 300,000 accounts (and growing), what are the pros and cons of using a schema per account to partition the data vs putting all the ...
6
votes
1answer
188 views

Many-to-many relationship with attributes

I'm working on a project where I need a book database. The problem is as follows: A book can be related to multiple people (authors, editors, traslators, etc.). Then a person may contribute to ...
6
votes
1answer
389 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 ...
6
votes
1answer
6k views

Could too many idle connections affect PostgreSQL 9.2 performance?

Some queries on my database server seem to take a long time to respond, and I believe the CPU usage is high. When running ps aux, I see ~250 "idle" connections (which I believe to be too many). I ...
6
votes
2answers
4k views

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
votes
1answer
185 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
votes
1answer
1k views

Designing a database for a site that stores content from multiple services?

I'm building a site that implements David Allen's Getting Things Done that pulls in your email, Facebook newsfeed, tweets from those you follow on Twitter, and more services are planned. The problem ...
6
votes
1answer
69 views

Is it useful to split a table into a frequently used and a archive table?

I have a table with 1.000.000+ entries. Only the newest 100.000 entries are used very frequently. The other 90% are used very seldom. Is it useful to split this table into a frequently used table ...
6
votes
1answer
131 views

MySQL database design to sort and filter air traffic data

I am struggling to design the correct database / structure for what I'm trying to do. Let me try and explain the situation. Background We are a group of enthusiasts who monitor air traffic via ...
6
votes
2answers
1k views

Database table design question

Firstly, database novice here. I'm trying to create a system for processing Sales Orders into Purchase Orders and then split the Purchase Order into Shipping Containers. The systems needs to be able ...
6
votes
1answer
3k views

Schema design: Use of association (aka: bridge/junction) table vs foreign key constraint with composite index containing a non-key field

This is an inventory database for IT assets. The models used are trimmed in order to focus on the problem at hand. Using SQL Server 2008. Thanks for taking the time to read and for any input you can ...
6
votes
1answer
699 views

ERWIN create and use database

I'm trying to generate physical database from my logical model using ERWIN 7. All is well in the script that is generated automatically, there is only the problem that the model is created in the ...
6
votes
4answers
501 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 ...
6
votes
1answer
332 views

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 ...
6
votes
2answers
244 views

Single table with more columns vs multiple tables with fewer columns

What would be a better database design for a social network website? A single table with more columns and fewer rows, or multiple tables with fewer columns but more rows? For example: A user can post ...
5
votes
8answers
4k views

Should you ever not assign an unique ID to each row in a table? [duplicate]

Possible Duplicate: Should every table have a single-field surrogate/artificial primary key? I can't imagine ever not using a unique ID with every table, which is why I'm asking this ...
5
votes
6answers
6k views

Any way around unique index 16 column max

According to the CREATE INDEX documentation: Up to 16 columns can be combined into a single composite index key. We've got a table with ~18 columns that need to form a unique combination. This ...
5
votes
2answers
498 views

Likes or votes for posts

I am making a small program where users makes posts or write blogs. On those posts, other users can like or dislike the post as in facebook or upvote or downvote the post as in stackoverflow. I would ...
5
votes
3answers
812 views

Is a surrogate key better than a natural key in this case

I copied this code from here: CREATE TABLE records( email TEXT REFERENCES users(email), lat DECIMAL, lon DECIMAL, depth TEXT, upload_date TIMESTAMP, comment TEXT, PRIMARY ...
5
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2answers
872 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 ...
5
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4answers
3k views

Examples of SQL transaction procedures for sales tracking or a financial database

I am making a database for an accounting/sales type system similar to a car sales database and would like to make some transactions for the following real world actions: salesman creates new product ...