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  2. Set operations (SQL) - Wikipedia

    en.wikipedia.org/wiki/Set_operations_(SQL)

    In SQL the UNION clause combines the results of two SQL queries into a single table of all matching rows. The two queries must result in the same number of columns and compatible data types in order to unite. Any duplicate records are automatically removed unless UNION ALL is used.

  3. 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.

  4. List of SQL reserved words - Wikipedia

    en.wikipedia.org/wiki/List_of_SQL_reserved_words

    Reserved words in SQL and related products In SQL:2023 [3] In IBM Db2 13 [4] In Mimer SQL 11.0 [5] In MySQL 8.0 [6] In Oracle Database 23c [7] In PostgreSQL 16 [1] In Microsoft SQL Server 2022 [2]

  5. Multiset - Wikipedia

    en.wikipedia.org/wiki/Multiset

    A multiset may be formally defined as an ordered pair (A, m) where A is the underlying set of the multiset, formed from its distinct elements, and : + is a function from A to the set of positive integers, giving the multiplicity – that is, the number of occurrences – of the element a in the multiset as the number m(a).

  6. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...

  7. Trump to prepare facility at Guantanamo for 30,000 migrants - AOL

    www.aol.com/news/trump-says-instruct-homeland...

    WASHINGTON (Reuters) -U.S. President Donald Trump said on Wednesday he will order the Pentagon and the Department of Homeland Security to prepare a migrant detention facility at Guantanamo Bay for ...

  8. Disjoint-set data structure - Wikipedia

    en.wikipedia.org/wiki/Disjoint-set_data_structure

    In computer science, a disjoint-set data structure, also called a union–find data structure or merge–find set, is a data structure that stores a collection of disjoint (non-overlapping) sets. Equivalently, it stores a partition of a set into disjoint subsets .

  9. “Arrest The Parents For Neglect”: Woman Who Says She’s ...

    www.aol.com/polish-woman-claiming-madeleine...

    Image credits: _amijuliawandelt Julia later expressed regret over declaring on Instagram that she was Madeleine McCann and went on to apologize to the McCanns for possibly adding to their misery.