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2. Relational algebra - Wikipedia

   en.wikipedia.org/wiki/Relational_algebra

   The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.

3. Category:Relational algebra - Wikipedia

   en.wikipedia.org/wiki/Category:Relational_algebra

   Download QR code; Print/export Download as PDF; Printable version; In other projects Wikimedia Commons; Wikidata item; ... Pages in category "Relational algebra"

4. Relation algebra - Wikipedia

   en.wikipedia.org/wiki/Relation_algebra

   A relation algebra (L, ∧, ∨, −, 0, 1, •, I, ˘) is an algebraic structure equipped with the Boolean operations of conjunction x∧y, disjunction x∨y, and negation x −, the Boolean constants 0 and 1, the relational operations of composition x•y and converse x˘, and the relational constant I, such that these operations and constants satisfy certain equations constituting an ...

5. Category:Relational model - Wikipedia

   en.wikipedia.org/wiki/Category:Relational_model

   Download QR code; Print/export Download as PDF; Printable version; In other projects Wikimedia Commons; Wikidata item; ... Relational algebra; Relational calculus;

6. Codd's theorem - Wikipedia

   en.wikipedia.org/wiki/Codd's_theorem

   Codd's theorem states that relational algebra and the domain-independent relational calculus queries, two well-known foundational query languages for the relational model, are precisely equivalent in expressive power. That is, a database query can be formulated in one language if and only if it can be expressed in the other.

7. Greek letters used in mathematics, science, and engineering

   en.wikipedia.org/wiki/Greek_letters_used_in...

   the unary projection operation in relational algebra; the Pi function, i.e. the Gamma function when offset to coincide with the factorial; the complete elliptic integral of the third kind; the fundamental groupoid; osmotic pressure; represents:

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9. Restriction (mathematics) - Wikipedia

   en.wikipedia.org/wiki/Restriction_(mathematics)

   In relational algebra, a selection (sometimes called a restriction to avoid confusion with SQL's use of SELECT) is a unary operation written as or () where: a {\displaystyle a} and b {\displaystyle b} are attribute names,