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8
votes
4answers
356 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
283 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
268 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 ...
5
votes
2answers
2k 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
191 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
549 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
202 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 ...
8
votes
3answers
7k 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
679 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
830 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
2k 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 ...
54
votes
5answers
21k 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 ...
4
votes
1answer
677 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. ...
19
votes
1answer
702 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
379 views

Pioneers in Database Research

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