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2. Projection (relational algebra) - Wikipedia

   en.wikipedia.org/.../Projection_(relational_algebra)

   In practical terms, if a relation is thought of as a table, then projection can be thought of as picking a subset of its columns. For example, if the attributes are (name, age), then projection of the relation {(Alice, 5), (Bob, 8)} onto attribute list (age) yields {5,8} – we have discarded the names, and only know what ages are present.

3. Selection (relational algebra) - Wikipedia

   en.wikipedia.org/wiki/Selection_(relational_algebra)

   Mutation and Selection. In relational algebra, a selection (sometimes called a restriction in reference to E.F. Codd's 1970 paper [1] and not, contrary to a popular belief, to avoid confusion with SQL's use of SELECT, since Codd's article predates the existence of SQL) is a unary operation that denotes a subset of a relation.

4. 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.

5. Relation algebra - Wikipedia

   en.wikipedia.org/wiki/Relation_algebra

   In mathematics and abstract algebra, a relation algebra is a residuated Boolean algebra expanded with an involution called converse, a unary operation.The motivating example of a relation algebra is the algebra 2 X 2 of all binary relations on a set X, that is, subsets of the cartesian square X 2, with R•S interpreted as the usual composition of binary relations R and S, and with the ...

6. Hallmark Star John Reardon Reveals Tonsil Cancer Diagnosis ...

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   John Reardon revealed that he was diagnosed with tonsil cancer.. On Dec. 24, the Hallmark actor, 49, posted two photos on Instagram while sharing the health news. The post included a photo of the ...

7. Category:Relational algebra - Wikipedia

   en.wikipedia.org/wiki/Category:Relational_algebra

   Projection (relational algebra) R. ... Selection (relational algebra) String operations This page was last edited on 24 December 2022, at 00:30 (UTC) ...

8. Man Asks Girlfriend's Golden Retriever Puppy for Permission ...

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   An adorable TikTok video of Matt asking for the then six-month-old golden retriever's permission went viral just days after his proposal at Lookout Mountain Park in Colorado on Nov. 9, 2021. The ...

9. Sweet Rottweiler's Friendship with Neighbor Takes Unexpected ...

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   Follow us on YouTube for more entertaining videos. Or, share your own adorable pet by submitting a video, and sign up for our newsletter for the latest pet updates and tips. Show comments.