3
votes
1answer
72 views

What does the “structured” in Structured Query Language mean?

What makes SQL "structured"? Are structured query languages distinguishable from unstructured ones? And when we say that SQL is "declarative", is that a related concept?
0
votes
0answers
33 views

Decomposition into BCNF where an attribute appears in multiple functional dependencies

I am trying to decompose my relation: R = (A, B, C, D, E) with Functional Dependencies F = {D -> BC, E -> B, A -> B, B -> D} The problem is that D appears in two dependencies and in ...
6
votes
1answer
745 views

Find the highest graded student, using Tuple Relational Calculus

Suppose I have a table of students, containing their ID and their grade: ----------------- | id | grade | ----------------- | 1 | 83 | | 2 | 94 | | 3 | 92 | | 4 | 78 | ...
0
votes
3answers
91 views

Column partially determining accepted values of another column, should be somehow normalized?

I have a table that describes a set of properties (yes it's metadata, in this case there's a valid reason to have it in the database); among other things I tell the type of the data that can be ...
1
vote
0answers
100 views

Closure of attributes definition clarification

A databases book I am using states [1]: The closure of {A1, A2, ..., An} under the FD's in S is the set of attributes B such that every relation that satisfies all the FD's in set S also satisfies ...