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  2. Cardinality (SQL statements) - Wikipedia

    en.wikipedia.org/wiki/Cardinality_(SQL_statements)

    Low-cardinality column values are typically status flags, Boolean values, or major classifications such as gender. An example of a data table column with low-cardinality would be a CUSTOMER table with a column named NEW_CUSTOMER. This column would contain only two distinct values: Y or N, denoting whether the customer was new or not.

  3. Essentially unique - Wikipedia

    en.wikipedia.org/wiki/Essentially_unique

    There is an essentially unique two-dimensional, compact, simply connected manifold: the 2-sphere. In this case, it is unique up to homeomorphism. In the area of topology known as knot theory, there is an analogue of the fundamental theorem of arithmetic: the decomposition of a knot into a sum of prime knots is essentially unique. [5]

  4. Join (SQL) - Wikipedia

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

    The natural join can be simulated with Codd's primitives as follows. Let c 1, ..., c m be the attribute names common to R and S, r 1, ..., r n be the attribute names unique to R and let s 1, ..., s k be the attributes unique to S. Furthermore, assume that the attribute names x 1, ..., x m are neither in R nor in S.

  5. Uniqueness quantification - Wikipedia

    en.wikipedia.org/wiki/Uniqueness_quantification

    In mathematics and logic, the term "uniqueness" refers to the property of being the one and only object satisfying a certain condition. [1] This sort of quantification is known as uniqueness quantification or unique existential quantification, and is often denoted with the symbols "∃!" [2] or "∃ =1". For example, the formal statement

  6. Unique key - Wikipedia

    en.wikipedia.org/wiki/Unique_key

    In relational database management systems, a unique key is a candidate key. All the candidate keys of a relation can uniquely identify the records of the relation, but only one of them is used as the primary key of the relation. The remaining candidate keys are called unique keys because they can uniquely identify a record in a relation.

  7. Set (abstract data type) - Wikipedia

    en.wikipedia.org/wiki/Set_(abstract_data_type)

    In computer science, a set is an abstract data type that can store unique values, without any particular order. It is a computer implementation of the mathematical concept of a finite set. Unlike most other collection types, rather than retrieving a specific element from a set, one typically tests a value for membership in a set.

  8. Relation of degree zero - Wikipedia

    en.wikipedia.org/wiki/Relation_of_degree_zero

    [1]:57 Under the closed-world assumption, an n-ary relation is interpreted as the extension of some n-adic predicate: all and only those n-tuples whose values, substituted for corresponding free variables in the predicate, yield propositions that hold true, appear in the relation.

  9. Monogenēs - Wikipedia

    en.wikipedia.org/wiki/Monogenēs

    For example, o monogenēs means "the only one", or "the only legitimate child". [4] The word is used in Hebrews 11:17–19 to describe Isaac, the son of Abraham. However, Isaac was not the only-begotten son of Abraham, but was the chosen, having special virtue. [5] Thus Isaac was "the only legitimate child" of Abraham.