The Thaumatorium:
Where the magic happens

# Articles

This article contains the symbols I've found in a video from CMU Database Group, a YT channel from Carnegie Mellon University.

## Basic Relational Algebra Operators

σ (Selection)
Symbol: σ (Sigma)
Description: The Selection operator is used to filter rows based on a specified condition.
Example: σ(condition)(relation)
π (Projection)
Symbol: π (Pi)
Description: The Projection operator selects specific columns from a table.
Example: π(column1, column2, ...)(relation)
∪ (Union)
Symbol: ∪ (Union)
Description: The Union operator combines the results of two tables, removing duplicates.
Example: relation1 ∪ relation2
∩ (Intersection)
Symbol: ∩ (Intersection)
Description: The Intersection operator returns only the rows that are present in both tables.
Example: relation1 ∩ relation2
− (Difference)
Symbol: − (Minus or Difference)
Description: The Difference operator returns the rows present in the first table but not in the second.
Example: relation1 − relation2
× (Cartesian Product)
Symbol: × (Cross or Cartesian Product)
Description: The Cartesian Product operator returns the Cartesian product of two tables.
Example: relation1 × relation2
⨝ (Join)
Symbol: ⨝ (Join)
Description: The Join operator combines rows from two tables based on a related column.
Example: relation1 ⨝ relation2

ρ (Rename)
Symbol: ρ (Rho)
Description: The Rename operator is used to rename the relation or attributes.
Example: ρ(new_name)(relation)
← (Assignment)
Symbol: R ← S (Assignment)
Description: The Assignment operator is used to assign the result of a query to a relation variable.
Example: R ← σ(condition)(relation)
δ (Duplicate Elimination)
Symbol: δ (Delta)
Description: The Duplicate Elimination operator removes duplicate rows from a relation.
Example: δ(relation)
γ (Aggregation)
Symbol: γ (Gamma)
Description: The Aggregation operator is used for aggregate functions such as SUM, COUNT, AVG, etc.
Example: γ(attribute, SUM(attribute))(relation)
τ (Sorting)
Symbol: τ (Tau)
Description: The Sorting operator sorts the relation by specified attributes.
Example: τ(attribute)(relation)
÷ (Division)
Symbol: ÷ (Division)
Description: The Division operator is used to find tuples in one relation that are related to all tuples in another relation.
Example: relation1 ÷ relation2

## Sources

"F2023 #01 - Relational Model & Algebra (CMU Intro to Database Systems)" by CMU Database Group: