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1
vote
1answer
173 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 ...
7
votes
3answers
5k 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
632 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
760 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 ...
50
votes
5answers
17k 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
551 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. ...
18
votes
1answer
658 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
378 views

Pioneers in Database Research

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