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2
votes
1answer
273 views

Deriving formulas for input/output

I'm currently enrolled in a DBS class and am having problem with an assignment. I've searched around and have been unable to understand what it is I'm meant to be doing with this derivation formula. ...
0
votes
2answers
1k views

Keep total transaction in invoice application

I want to make an application called as Invoice Application with MySQL database. Now I have designed this database. Now I want to know is this database good for Invoice Application. I will use MySQL ...
1
vote
1answer
3k views

Planning simple CMS: How much relation?

I'm currently in the process of designing the database for a rather minimalistic Content Management System I'm working on alone. It should allow scalability while remaining speed, especially on boxes ...
-1
votes
2answers
270 views

Information sources for multiple hierachy trees in a single table

I need some quality sources - books, websites etc. - to educate myself about putting multiple hierarchy trees in a single table using SQL. I'm looking for some good theoretical and practical ...
0
votes
1answer
147 views

Database column vs row size

I have Column A and Column B in a single table. I need to add 1,000,000 records to this table. I have 2 options: Keep 2 columns and add 1,000,000 records Add more columns and flatten out the ...
3
votes
2answers
334 views

how is synchronization maintained between different write and read database

One of my friends was asked this question in interview. Given two different databases one on which only write is done and the other on which only read is done. How does one maintain synchronization ...
4
votes
5answers
3k views

Does 'Cities' deserve a separate table?

I have the following Customers table: customer_id - int company_name - nvarchar street - nvarchar city - nvarchar comments - nvarchar The app will only be used in part of one small country ...
4
votes
1answer
3k views

Under what conditions are polymorphic associations used? What are the alternatives?

As I understand it, polymorphic relationships among tables in a database allow one table to have one foreign key that references many tables. I have found that tags are a common application of this ...
3
votes
4answers
187 views

Complete list of possible database “objects”?

When I finished my degree in Programming and Database I remember there being a general list of database "objects" like this: data types (a list unto itself) fields records tables views (sort of like ...
8
votes
4answers
372 views

What is a database?

There was lot of discussion in this question: What database technologies do big search engines use? So much discussion that it made me confused. So... what is a database, anyway? Are only relational ...
3
votes
1answer
299 views

to what “scale” of applications does nosql support?

Recently i came across the Nosql database concept, though i learnt how to and why of it, i did not get a proper answer to the question , to what scale of project does it support? Will it support ...
2
votes
1answer
292 views

Postgres synchronized backup - what's with the archive?

I am setting up a Postgres 9.1 master and a hot standby-server. I read the documentation but I'm not quite sure yet what I should do with my WAL files. Every commit is done on both servers before ...
10
votes
2answers
3k views

Ready-to-Use Database models example

Where can I find ready-to-use database models ? I don't need a database with data in it, but only schemas (UML diagrams). Perhaps something like the data models at this link, but much more complex ...
1
vote
1answer
199 views

Is an anomaly free relation necessarily normalized?

A normalized relation can still suffer anomalies. Going the other way, which (if any) normal forms can be violated by a relation that's free from anomalies? If such exist, For each such normal form ...
0
votes
3answers
661 views

SQL Server : primary keys advice to my whitepaper needed

I've tired to explain to every new junior developer in our r&d team why he should use Primary Keys and how to do that. So I decided to write small whitepaper, which every new developer should ...
1
vote
1answer
243 views

Overlapping Transactions

Apolgies in advance if this has been discussed before, or is even fundamental enough for it to be outlined on, say, Wikipedia. I just felt that asking would be more efficient! Anyway, I want to ask ...
13
votes
4answers
11k views

Why are NULLs sorted first?

Why is it that when we have a NULL value in a column and we order by the value ascending, the NULLs are sorted first? select 1 as test union all select 2 union all select NULL union all select 3 ...
7
votes
1answer
757 views

Is DB Normalization done purely based on the primary key or is it done based on all the candidate keys?

I have come across two flavours of the normalization procedure while referring the internet and textbooks. viz. Type 1. Normal forms based only on the primary key. In this type, -> 2NF disallows ...
4
votes
2answers
931 views

Right Full Outer Join Query

I came across 1 query which is Select * from R Natural Outer Join S Where R=(A,B) has tuples {(1,2),(1,2),(3,4)} and S=(B,C) has tuples {(2,5),(2,5),(4,6),(7,10)}. To implement this I created 2 ...
3
votes
2answers
3k views

Does the SELECT statement count into DML?

Looking at the name Data Manipulation Language (DML) I would assume, that all contained statements are actually for manipulating data. As far as I know the SELECT statement can only be used to query ...
65
votes
5answers
29k views

When to use TINYINT over INT?

In general, I always use Ints. I know that in theory this is not the best practice, though, since you should use the smallest data type that will be guaranteed to store the data. For example, it's ...
5
votes
1answer
852 views

Transaction and data consistency during a failure

When a database begins a transaction, all statements executed in that transaction are isolated and atomic (and consistent and durable). These are pretty much the definition of a transaction. ...
20
votes
1answer
774 views

What is the reasoning behind the CAP theorem?

http://en.wikipedia.org/wiki/CAP_theorem http://www.cs.berkeley.edu/~brewer/cs262b-2004/PODC-keynote.pdf I think it is not very straightforward why only two of Consistency Availability Partition ...
10
votes
8answers
392 views

Pioneers in Database Research

Who all people have made life changing contributions to database research? I want to know more about them.