MHB Relational algebra - What does "in" mean and how is it different than "="?

  • Thread starter Thread starter find_the_fun
  • Start date Start date
  • Tags Tags
    Algebra Mean
Click For Summary
In relational algebra, "in" signifies membership, indicating that an element belongs to a set or relation. The expression σ_{car IN car}R suggests that "car" is being evaluated against a set of values within relation R. The syntax used can vary based on the context, such as the specific software or textbook referenced. Typically, atomic formulas in relational algebra involve comparisons between attributes or constants, and "car IN car" likely represents a comparison where the first "car" is an attribute and the second is a collection of values. Understanding the precise meaning of "in" requires context regarding the specific relational algebra framework being discussed.
find_the_fun
Messages
147
Reaction score
0
In relational algebra what does "in" mean?
For example
[math]\sigma_{car IN car}R[/math] where R is some relation.
 
Mathematics news on Phys.org
Do you mean:

$\displaystyle \sigma\in\mathbb{R}$ ?

If so, the "in" means "is an element of."

edit: I just noticed this is probably not what you are referring to! (Doh)
 
find_the_fun said:
In relational algebra what does "in" mean?
For example
[math]\sigma_{car IN car}R[/math] where R is some relation.
The subscript after σ is a formula. The exact syntax of such formulas depends on the context (software, textbook, etc.). As Wikipedia explains, a typical case is when atomic formulas have the form xRy where x is an attribute name, y is an attribute name or a constant, R is a relation such as <, and atomic formulas are joined by logical connectives. The formula "car IN car" is probably an atomic formula. Maybe the first "car" is an attribute name and the second "car" is an array of values. For a more precise answer one needs the context.
 

Thread 'Area of Overlapping Squares'

Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?
View full post »

Similar threads

Undergrad The adjective "finite" applied to algebraic structures
  • · Replies 4 ·
Replies
4
Views
1K
High School Solving equations but getting an identity - what mistakes were made?
  • · Replies 4 ·
Replies
4
Views
1K
High School What does 2:3 ratio mean? What does it show?
  • · Replies 9 ·
Replies
9
Views
3K
Undergrad Meaning of "identify" & variations in different math context
  • · Replies 5 ·
Replies
5
Views
929
Undergrad Meaning of "passage to the quotient"?
  • · Replies 3 ·
Replies
3
Views
862
What is the geometric approach to mathematical research?
  • · Replies 2 ·
Replies
2
Views
1K
MHB Which mean is larger when using algebraic expressions, A. M. or R. M. S.?
  • · Replies 13 ·
Replies
13
Views
3K
What does it mean to "do mathematics"?
  • · Replies 10 ·
Replies
10
Views
2K
High School What's the difference? "Types" of Algebra, etc
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Meaning of ##\coprod_{x\in\mathrm{Spec}R}R/\mathfrak{p}_x##
  • · Replies 11 ·
Replies
11
Views
1K