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What are the additional operations in relational algebra ?

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By Dipali Umre

Set Intersection Operation (⋂):

  • This operation returns a relation with tuples that exist in both input relations.
  • Written as r ⋂ s = r - (r - s), where - represents set difference.
  • In simpler terms, it gives you common elements between two sets.

Natural Join Operation (⨝):

  • Combines two relations based on matching attributes.
  • Forms a cartesian product, applies a selection on common attributes, and removes duplicates.
  • Denoted by the join symbol ⨝.
  • In simpler terms, it’s like combining two sets where certain attributes are equal.

Division Operation (÷):

  • Denoted by the symbol ÷.
  • Given two relations, r ÷ s produces a relation on the schema R – S.
  • A tuple is in the result if it satisfies specific conditions related to projection and matching attributes.
  • Essentially, it represents a kind of filtering or extracting operation based on certain conditions.

Assignment Operation (←):

  • Denoted by the symbol ←.
  • Similar to assignment in programming languages, it allows you to store the result of a relational algebra expression into a variable.
  • Useful for simplifying complex expressions and improving readability.

These operations provide a way to manipulate and combine relations in a relational database, helping to express more complex queries and operations.

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