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Mar
2
comment Question about choosing primary key
PersonID and EmployeeID are both keys in Employee. On that basis there is no violation of 3NF.
Feb
18
answered Can we determine FDs if we are given some tuples?
Feb
3
comment If A and B are candidate keys, then AB is candidate key or not ?
ab doesn't mean the intersection of the domains a and b, it means the superkey {a,b}. That might have been clearer if the OP had put parentheses around it but the question is clearly about keys and superkeys.
Jan
5
comment Why should I create an ID column when I can use others as key fields?
If criminals are known to clone some identifier then surely that might be a very good reason to enforce the business rule that the attribute must be unique - i.e. not to "trip up" the system but to prevent the said duplicate values from entering the database and thereby red-flag any such attempts as potential fraud or errors requiring further investigation.
Nov
19
answered does the mere existence of a primary key increase query speed for large data sets?
Nov
7
comment Uniqueidentifier vs. IDENTITY vs. Material Code --which is the best choice for primary key?
There is nothing purely "philosophical" about the need to identify real things accurately and to guarantee the uniqueness of meaningful data through key constraints. Natural keys are a very practical necessity.
Nov
3
revised What exactly is overlapping candidate key?
added 35 characters in body
Nov
3
answered What exactly is overlapping candidate key?
Apr
11
answered Given the functional dependencies of a relation is there more then one way to normalize it?
Mar
31
awarded  Yearling
Mar
21
comment Confusion with Foreign Keys
There's no reason in principle why primary key attributes shouldn't be foreign keys.
Mar
5
comment Column suitable for natural key?
@mircale, my point was that the reason for key constraints is to guarantee that infomration is not duplicated. If you don't enforce a natural key on some attribute then the values of that attribute may be duplicated on multiple tuples with different surrogate key values. That is apparently not what is wanted here.
Mar
3
answered Column suitable for natural key?
Feb
25
answered Is matriculation number a good primary key?
Jan
4
comment Primary Key Question
"if I have a key of FirstName, LastName, Email on my Student table, and then have to repeat that information in my Classes table then I'm duplicating data in that table and breaking one of the normal forms. Is that not correct?" That is not correct. In any case it's a poor example because it seems highly unlikely that firstname and lastname would be part of a key for students in any real or practical sense.
Nov
25
revised Platform independent select ordered by primary key
added 935 characters in body
Nov
25
revised Platform independent select ordered by primary key
deleted 1 characters in body
Nov
25
answered Platform independent select ordered by primary key
Nov
1
comment If all variables are a subset of the candidate key, is the database design 5NF?
Damir, you are right and my answer is wrong. I don't know what I was thinking of - BCNF maybe. Thanks anyway.
Oct
31
comment Is normalization process needed?
Perhaps it would be better to say that we should normalize the logical structure of the database. The phrase "logical model" is often (mis)understood to mean merely a preliminary design for a database rather than something actually existing in a database system. The important point surely is that what you implement ought to be normalized, not just what you sketch on paper :)