What normal form is violated here?
What could fix the problem?
A telephone call is uniquely identified by telephone number and time of call.
These candidate keys compose the composite primary key. There is another

Googling out for definition and explanation for sixth normal form only
resulted in the following information - "6th normal form states that a
relation R should not contain any non-trivial join dependencies". Also
everywhere it is stated that this normal form takes into account the

I have a database with individuals in it, and I'd like to store their
kin relationships also.
A quick, clumsy way of doing it would be to have three columns:  two
for individuals, and the third expressing their relationship (e.g. 'a

I realize that the following questions might seem totally irrelevant
to most of you, but I'm still hoping someone will take the time to
answer them.
BTW - I will use IS for information system

a)
Weak entity type cannot be uniquely identified by its own attributes
alone and thus needs another entity to be uniquely identified.
So in relational model, every relation which has primary key made of

I would really need some help with the following questions. And
apologies for so many of them
1)
a)

An extract from a post on experts-exchange.com (gosh I miss the quote
of the week by Fabian PASCAL) ..A sign of our times...I invited Scott
Pletchers to come explain how a primary is both a physical and logical
concept...I am curious to see if he will join in...

I am working on a project that intends to investigate the
implementation of a modern heuristic  (e.g. simulated annealing,
genetic algorithms or local search) to search through a space of
polynomial transformations and assign selections for a linear

One simplistic method of trying to distinguish multiple meanings possibly
associated with NULL is to associate particular non-NULL meanings with those
values.
For example, I might want to store both "unknown" and "known, but not yet

I would really need some help here
Some time ago I made a thread about cardinality and thought I
understood it , but today I noticed that I actually misread a post
explaining cardinality and realized that the subject still very much

I believe Codd originally envisaged "tables" that had what he called
domain names to identify "columns" but that in his second paper, he
introduced what we know of as attribute names because he wanted, for
example, to allow for relations between things of the same type, such as

can someone tell me (or point me in the right direction) of what the
right way of finding duplicates in dirty data (caused by typo's) ?
is there something like a 'hashing' or 'rating' of text that will give
you a number that you can compare ?

When we execute SELECT statement, the following steps are taken:
1) temporary table ( call it T ) is created
2) the number of rows T has equals to all possible combinations with
which the rows from the two tables can be joined ( assuming there are