- uniqueness constraint
- A constraint that prohibits repetition of individual data or combinations of data.قيد تفرد
English-Arabic terms dictionary. 2015.
English-Arabic terms dictionary. 2015.
Document Type Definition — (DTD) is a set of markup declarations that define a document type for SGML family markup languages (SGML, XML, HTML). DTDs were a precursor to XML schema and have a similar function, although different capabilities. DTDs use a terse formal syntax … Wikipedia
Natural key — In relational model database design, a natural key is a candidate key that has a logical relationship to the attributes within that row. A natural key is sometimes called a domain key. The main advantage of a natural key over a surrogate key,… … Wikipedia
Cognitive Constraints on Compositional Systems — Fred Lerdahl s Cognitive Constraints on Compositional Systems cites Pierre Boulez s Le Marteau sans Maître (1955) as an example of a huge gap between compositional system and cognized result, though he could have illustrated just as well with… … Wikipedia
Null (SQL) — The Greek lowercase omega (ω) character is used to represent Null in database theory. Null is a special marker used in Structured Query Language (SQL) to indicate that a data value does not exist in the database. Introduced by the creator of the… … Wikipedia
Unique key — In relational database design, a unique key can uniquely identify each row in a table, and is closely related to the Superkey concept. A unique key comprises a single column or a set of columns. No two distinct rows in a table can have the same… … Wikipedia
Candidate key — In the relational model, a candidate key of a relvar (relation variable) is a set of attributes of that relvar such that # at all times it holds in the relation assigned to that variable that there are no two distinct tuples with the same values… … Wikipedia
Group (mathematics) — This article covers basic notions. For advanced topics, see Group theory. The possible manipulations of this Rubik s Cube form a group. In mathematics, a group is an algebraic structure consisting of a set together with an operation that combines … Wikipedia
Ingres (database) — Ingres Ingres Corporation logo Developer(s) Actian Corporation Stable release Ingres Database 10 / October 12, 2010; 13 months ago (2010 10 12) … Wikipedia
Coherent diffraction imaging — A diffraction pattern of a gold nanocrystal formed from using a nano area beam of coherent X rays. This reciprocal space diffraction image was taken by Ian Robinson s Group to be used in the reconstruction of a real space coherent x ray… … Wikipedia
Gödel numbering for sequences — A Gödel numbering for sequences provides us an effective way to represent each finite sequence of natural numbers as a single natural number. Of course, the embedding is surely possible set theoretically, but the emphasis is on the effectiveness… … Wikipedia
Principle of maximum entropy — This article is about the probability theoretic principle. For the classifier in machine learning, see maximum entropy classifier. For other uses, see maximum entropy (disambiguation). Bayesian statistics Theory Bayesian probability Probability… … Wikipedia